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diff --git a/Source/WebCore/rendering/RenderVTTCue.cpp b/Source/WebCore/rendering/RenderVTTCue.cpp
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+++ b/Source/WebCore/rendering/RenderVTTCue.cpp
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+/*
+ * Copyright (C) 2012 Victor Carbune (victor@rosedu.org)
+ * Copyright (C) 2014 Apple Inc.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
+ */
+
+#include "config.h"
+
+#if ENABLE(VIDEO_TRACK)
+#include "RenderVTTCue.h"
+
+#include "RenderView.h"
+#include "TextTrackCueGeneric.h"
+#include "VTTCue.h"
+#include <wtf/StackStats.h>
+
+namespace WebCore {
+
+RenderVTTCue::RenderVTTCue(VTTCueBox& element, RenderStyle&& style)
+    : RenderBlockFlow(element, WTFMove(style))
+    , m_cue(element.getCue())
+{
+}
+
+void RenderVTTCue::layout()
+{
+    StackStats::LayoutCheckPoint layoutCheckPoint;
+    RenderBlockFlow::layout();
+
+    // If WebVTT Regions are used, the regular WebVTT layout algorithm is no
+    // longer necessary, since cues having the region parameter set do not have
+    // any positioning parameters. Also, in this case, the regions themselves
+    // have positioning information.
+    if (!m_cue->regionId().isEmpty())
+        return;
+
+    LayoutStateMaintainer statePusher(view(), *this, locationOffset(), hasTransform() || hasReflection() || style().isFlippedBlocksWritingMode());
+    
+    if (m_cue->cueType()== TextTrackCue::WebVTT) {
+        if (toVTTCue(m_cue)->snapToLines())
+            repositionCueSnapToLinesSet();
+        else
+            repositionCueSnapToLinesNotSet();
+    } else
+        repositionGenericCue();
+
+    statePusher.pop();
+}
+
+bool RenderVTTCue::initializeLayoutParameters(InlineFlowBox*& firstLineBox, LayoutUnit& step, LayoutUnit& position)
+{
+    ASSERT(firstChild());
+    if (!firstChild())
+        return false;
+
+    RenderBlock* parentBlock = containingBlock();
+
+    // firstChild() returns the wrapping (backdrop) <div>. The cue object is
+    // the <div>'s first child.
+    RenderObject& firstChild = *this->firstChild();
+    RenderElement& backdropElement = downcast<RenderElement>(firstChild);
+    
+    firstLineBox = downcast<RenderInline>(*backdropElement.firstChild()).firstLineBox();
+    if (!firstLineBox)
+        firstLineBox = this->firstRootBox();
+
+    // 1. Horizontal: Let step be the height of the first line box in boxes.
+    //    Vertical: Let step be the width of the first line box in boxes.
+    step = m_cue->getWritingDirection() == VTTCue::Horizontal ? firstLineBox->height() : firstLineBox->width();
+
+    // 2. If step is zero, then jump to the step labeled done positioning below.
+    if (!step)
+        return false;
+
+    // 3. Let line position be the text track cue computed line position.
+    int linePosition = m_cue->calculateComputedLinePosition();
+
+    // 4. Vertical Growing Left: Add one to line position then negate it.
+    if (m_cue->getWritingDirection() == VTTCue::VerticalGrowingLeft)
+        linePosition = -(linePosition + 1);
+
+    // 5. Let position be the result of multiplying step and line position.
+    position = step * linePosition;
+
+    // 6. Vertical Growing Left: Decrease position by the width of the
+    // bounding box of the boxes in boxes, then increase position by step.
+    if (m_cue->getWritingDirection() == VTTCue::VerticalGrowingLeft) {
+        position -= width();
+        position += step;
+    }
+
+    // 7. If line position is less than zero...
+    if (linePosition < 0) {
+        // Horizontal / Vertical: ... then increase position by the
+        // height / width of the video's rendering area ...
+        position += m_cue->getWritingDirection() == VTTCue::Horizontal ? parentBlock->height() : parentBlock->width();
+
+        // ... and negate step.
+        step = -step;
+    }
+
+    return true;
+}
+
+void RenderVTTCue::placeBoxInDefaultPosition(LayoutUnit position, bool& switched)
+{
+    // 8. Move all boxes in boxes ...
+    if (m_cue->getWritingDirection() == VTTCue::Horizontal)
+        // Horizontal: ... down by the distance given by position
+        setY(y() + position);
+    else
+        // Vertical: ... right by the distance given by position
+        setX(x() + position);
+
+    // 9. Default: Remember the position of all the boxes in boxes as their
+    // default position.
+    m_fallbackPosition = FloatPoint(x(), y());
+
+    // 10. Let switched be false.
+    switched = false;
+}
+
+bool RenderVTTCue::isOutside() const
+{
+    return !rectIsWithinContainer(absoluteContentBox());
+}
+
+bool RenderVTTCue::rectIsWithinContainer(const IntRect& rect) const
+{
+    return containingBlock()->absoluteBoundingBoxRect().contains(rect);
+}
+
+
+bool RenderVTTCue::isOverlapping() const
+{
+    return overlappingObject();
+}
+
+RenderObject* RenderVTTCue::overlappingObject() const
+{
+    return overlappingObjectForRect(absoluteBoundingBoxRect());
+}
+
+RenderObject* RenderVTTCue::overlappingObjectForRect(const IntRect& rect) const
+{
+    for (RenderObject* box = previousSibling(); box; box = box->previousSibling()) {
+        IntRect boxRect = box->absoluteBoundingBoxRect();
+
+        if (rect.intersects(boxRect))
+            return box;
+    }
+
+    return 0;
+}
+
+bool RenderVTTCue::shouldSwitchDirection(InlineFlowBox* firstLineBox, LayoutUnit step) const
+{
+    LayoutUnit top = y();
+    LayoutUnit left = x();
+    LayoutUnit bottom = top + firstLineBox->height();
+    LayoutUnit right = left + firstLineBox->width();
+
+    // 12. Horizontal: If step is negative and the top of the first line
+    // box in boxes is now above the top of the video's rendering area,
+    // or if step is positive and the bottom of the first line box in
+    // boxes is now below the bottom of the video's rendering area, jump
+    // to the step labeled switch direction.
+    LayoutUnit parentHeight = containingBlock()->height();
+    if (m_cue->getWritingDirection() == VTTCue::Horizontal && ((step < 0 && top < 0) || (step > 0 && bottom > parentHeight)))
+        return true;
+
+    // 12. Vertical: If step is negative and the left edge of the first line
+    // box in boxes is now to the left of the left edge of the video's
+    // rendering area, or if step is positive and the right edge of the
+    // first line box in boxes is now to the right of the right edge of
+    // the video's rendering area, jump to the step labeled switch direction.
+    LayoutUnit parentWidth = containingBlock()->width();
+    if (m_cue->getWritingDirection() != VTTCue::Horizontal && ((step < 0 && left < 0) || (step > 0 && right > parentWidth)))
+        return true;
+
+    return false;
+}
+
+void RenderVTTCue::moveBoxesByStep(LayoutUnit step)
+{
+    // 13. Horizontal: Move all the boxes in boxes down by the distance
+    // given by step. (If step is negative, then this will actually
+    // result in an upwards movement of the boxes in absolute terms.)
+    if (m_cue->getWritingDirection() == VTTCue::Horizontal)
+        setY(y() + step);
+
+    // 13. Vertical: Move all the boxes in boxes right by the distance
+    // given by step. (If step is negative, then this will actually
+    // result in a leftwards movement of the boxes in absolute terms.)
+    else
+        setX(x() + step);
+}
+
+bool RenderVTTCue::switchDirection(bool& switched, LayoutUnit& step)
+{
+    // 15. Switch direction: Move all the boxes in boxes back to their
+    // default position as determined in the step above labeled default.
+    setX(m_fallbackPosition.x());
+    setY(m_fallbackPosition.y());
+
+    // 16. If switched is true, jump to the step labeled done
+    // positioning below.
+    if (switched)
+        return false;
+
+    // 17. Negate step.
+    step = -step;
+
+    // 18. Set switched to true.
+    switched = true;
+    return true;
+}
+
+void RenderVTTCue::moveIfNecessaryToKeepWithinContainer()
+{
+    IntRect containerRect = containingBlock()->absoluteBoundingBoxRect();
+    IntRect cueRect = absoluteBoundingBoxRect();
+
+    int topOverflow = cueRect.y() - containerRect.y();
+    int bottomOverflow = containerRect.maxY() - cueRect.maxY();
+
+    int verticalAdjustment = 0;
+    if (topOverflow < 0)
+        verticalAdjustment = -topOverflow;
+    else if (bottomOverflow < 0)
+        verticalAdjustment = bottomOverflow;
+
+    if (verticalAdjustment)
+        setY(y() + verticalAdjustment);
+
+    int leftOverflow = cueRect.x() - containerRect.x();
+    int rightOverflow = containerRect.maxX() - cueRect.maxX();
+
+    int horizontalAdjustment = 0;
+    if (leftOverflow < 0)
+        horizontalAdjustment = -leftOverflow;
+    else if (rightOverflow < 0)
+        horizontalAdjustment = rightOverflow;
+
+    if (horizontalAdjustment)
+        setX(x() + horizontalAdjustment);
+}
+
+bool RenderVTTCue::findNonOverlappingPosition(int& newX, int& newY) const
+{
+    newX = x();
+    newY = y();
+    IntRect srcRect = absoluteBoundingBoxRect();
+    IntRect destRect = srcRect;
+
+    // Move the box up, looking for a non-overlapping position:
+    while (RenderObject* box = overlappingObjectForRect(destRect)) {
+        if (m_cue->getWritingDirection() == VTTCue::Horizontal)
+            destRect.setY(box->absoluteBoundingBoxRect().y() - destRect.height());
+        else
+            destRect.setX(box->absoluteBoundingBoxRect().x() - destRect.width());
+    }
+
+    if (rectIsWithinContainer(destRect)) {
+        newX += destRect.x() - srcRect.x();
+        newY += destRect.y() - srcRect.y();
+        return true;
+    }
+
+    destRect = srcRect;
+
+    // Move the box down, looking for a non-overlapping position:
+    while (RenderObject* box = overlappingObjectForRect(destRect)) {
+        if (m_cue->getWritingDirection() == VTTCue::Horizontal)
+            destRect.setY(box->absoluteBoundingBoxRect().maxY());
+        else
+            destRect.setX(box->absoluteBoundingBoxRect().maxX());
+    }
+
+    if (rectIsWithinContainer(destRect)) {
+        newX += destRect.x() - srcRect.x();
+        newY += destRect.y() - srcRect.y();
+        return true;
+    }
+
+    return false;
+}
+
+void RenderVTTCue::repositionCueSnapToLinesSet()
+{
+    InlineFlowBox* firstLineBox;
+    LayoutUnit step;
+    LayoutUnit position;
+    if (!initializeLayoutParameters(firstLineBox, step, position))
+        return;
+
+    bool switched;
+    placeBoxInDefaultPosition(position, switched);
+
+    // 11. Step loop: If none of the boxes in boxes would overlap any of the boxes
+    // in output and all the boxes in output are within the video's rendering area
+    // then jump to the step labeled done positioning.
+    while (isOutside() || isOverlapping()) {
+        if (!shouldSwitchDirection(firstLineBox, step))
+            // 13. Move all the boxes in boxes ...
+            // 14. Jump back to the step labeled step loop.
+            moveBoxesByStep(step);
+        else if (!switchDirection(switched, step))
+            break;
+
+        // 19. Jump back to the step labeled step loop.
+    }
+
+    // Acommodate extra top and bottom padding, border or margin.
+    // Note: this is supported only for internal UA styling, not through the cue selector.
+    if (hasInlineDirectionBordersPaddingOrMargin())
+        moveIfNecessaryToKeepWithinContainer();
+}
+
+void RenderVTTCue::repositionGenericCue()
+{
+    ASSERT(firstChild());
+
+    // firstChild() returns the wrapping (backdrop) <div>. The cue object is
+    // the <div>'s first child.
+    RenderObject& firstChild = *this->firstChild();
+    RenderElement& backdropElement = downcast<RenderElement>(firstChild);
+    
+    InlineFlowBox* firstLineBox = downcast<RenderInline>(*backdropElement.firstChild()).firstLineBox();
+    if (static_cast<TextTrackCueGeneric*>(m_cue)->useDefaultPosition() && firstLineBox) {
+        LayoutUnit parentWidth = containingBlock()->logicalWidth();
+        LayoutUnit width = firstLineBox->width();
+        LayoutUnit right = (parentWidth / 2) - (width / 2);
+        setX(right);
+    }
+    repositionCueSnapToLinesNotSet();
+}
+
+void RenderVTTCue::repositionCueSnapToLinesNotSet()
+{
+    // 3. If none of the boxes in boxes would overlap any of the boxes in output, and all the boxes in
+    // output are within the video's rendering area, then jump to the step labeled done positioning below.
+    if (!isOutside() && !isOverlapping())
+        return;
+
+    // 4. If there is a position to which the boxes in boxes can be moved while maintaining the relative
+    // positions of the boxes in boxes to each other such that none of the boxes in boxes would overlap
+    // any of the boxes in output, and all the boxes in output would be within the video's rendering area,
+    // then move the boxes in boxes to the closest such position to their current position, and then jump
+    // to the step labeled done positioning below. If there are multiple such positions that are equidistant
+    // from their current position, use the highest one amongst them; if there are several at that height,
+    // then use the leftmost one amongst them.
+    moveIfNecessaryToKeepWithinContainer();
+    int x = 0;
+    int y = 0;
+    if (!findNonOverlappingPosition(x, y))
+        return;
+
+    setX(x);
+    setY(y);
+}
+
+} // namespace WebCore
+
+#endif