1 files changed, 68 insertions, 44 deletions

diff --git a/chromium/third_party/blink/renderer/core/layout/layout_box_model_object.cc b/chromium/third_party/blink/renderer/core/layout/layout_box_model_object.cc
index 1128e3f3cf1..f1c2dfea9dd 100644
--- a/chromium/third_party/blink/renderer/core/layout/layout_box_model_object.cc
+++ b/chromium/third_party/blink/renderer/core/layout/layout_box_model_object.cc
@@ -25,6 +25,7 @@
 
 #include "third_party/blink/renderer/core/layout/layout_box_model_object.h"
 
+#include "third_party/blink/renderer/core/dom/node_computed_style.h"
 #include "third_party/blink/renderer/core/frame/local_frame.h"
 #include "third_party/blink/renderer/core/frame/local_frame_view.h"
 #include "third_party/blink/renderer/core/html/html_body_element.h"
@@ -39,7 +40,7 @@
 #include "third_party/blink/renderer/core/paint/paint_layer.h"
 #include "third_party/blink/renderer/core/paint/paint_layer_scrollable_area.h"
 #include "third_party/blink/renderer/core/style/shadow_list.h"
-#include "third_party/blink/renderer/platform/length_functions.h"
+#include "third_party/blink/renderer/platform/geometry/length_functions.h"
 #include "third_party/blink/renderer/platform/scroll/main_thread_scrolling_reason.h"
 #include "third_party/blink/renderer/platform/transforms/transform_state.h"
 
@@ -97,18 +98,30 @@ bool LayoutBoxModelObject::UsesCompositedScrolling() const {
 }
 
 BackgroundPaintLocation LayoutBoxModelObject::GetBackgroundPaintLocation(
-    uint32_t* reasons) const {
-  bool has_custom_scrollbars = false;
+    uint32_t* main_thread_scrolling_reasons) const {
+  bool may_have_scrolling_layers_without_scrolling = IsLayoutView();
+  const auto* scrollable_area = GetScrollableArea();
+  bool scrolls_overflow = scrollable_area && scrollable_area->ScrollsOverflow();
+  if (!scrolls_overflow && !may_have_scrolling_layers_without_scrolling)
+    return kBackgroundPaintInGraphicsLayer;
+
+  // If we care about LCD text, paint root backgrounds into scrolling contents
+  // layer even if style suggests otherwise. (For non-root scrollers, we just
+  // avoid compositing - see PLSA::ComputeNeedsCompositedScrolling.)
+  if (IsLayoutView()) {
+    DCHECK(Layer()->Compositor());
+    if (!Layer()->Compositor()->PreferCompositingToLCDTextEnabled())
+      return kBackgroundPaintInScrollingContents;
+  }
+
   // TODO(flackr): Detect opaque custom scrollbars which would cover up a
   // border-box background.
-  if (PaintLayerScrollableArea* scrollable_area = GetScrollableArea()) {
-    if ((scrollable_area->HorizontalScrollbar() &&
-         scrollable_area->HorizontalScrollbar()->IsCustomScrollbar()) ||
-        (scrollable_area->VerticalScrollbar() &&
-         scrollable_area->VerticalScrollbar()->IsCustomScrollbar())) {
-      has_custom_scrollbars = true;
-    }
-  }
+  bool has_custom_scrollbars =
+      scrollable_area &&
+      ((scrollable_area->HorizontalScrollbar() &&
+        scrollable_area->HorizontalScrollbar()->IsCustomScrollbar()) ||
+       (scrollable_area->VerticalScrollbar() &&
+        scrollable_area->VerticalScrollbar()->IsCustomScrollbar()));
 
   // TODO(flackr): When we correctly clip the scrolling contents layer we can
   // paint locally equivalent backgrounds into it. https://crbug.com/645957
@@ -119,8 +132,10 @@ BackgroundPaintLocation LayoutBoxModelObject::GetBackgroundPaintLocation(
   // painting into the composited scrolling contents layer.
   // https://crbug.com/646464
   if (StyleRef().BoxShadow()) {
-    if (reasons)
-      *reasons |= MainThreadScrollingReason::kHasBoxShadowFromNonRootLayer;
+    if (main_thread_scrolling_reasons) {
+      *main_thread_scrolling_reasons |=
+          MainThreadScrollingReason::kHasBoxShadowFromNonRootLayer;
+    }
     return kBackgroundPaintInGraphicsLayer;
   }
 
@@ -144,13 +159,17 @@ BackgroundPaintLocation LayoutBoxModelObject::GetBackgroundPaintLocation(
       if (clip == EFillBox::kBorder) {
         if (!has_custom_scrollbars &&
             (StyleRef().BorderTopWidth() == 0 ||
-             !ResolveColor(GetCSSPropertyBorderTopColor()).HasAlpha()) &&
+             (!ResolveColor(GetCSSPropertyBorderTopColor()).HasAlpha() &&
+              StyleRef().BorderTopStyle() == EBorderStyle::kSolid)) &&
             (StyleRef().BorderLeftWidth() == 0 ||
-             !ResolveColor(GetCSSPropertyBorderLeftColor()).HasAlpha()) &&
+             (!ResolveColor(GetCSSPropertyBorderLeftColor()).HasAlpha() &&
+              StyleRef().BorderLeftStyle() == EBorderStyle::kSolid)) &&
             (StyleRef().BorderRightWidth() == 0 ||
-             !ResolveColor(GetCSSPropertyBorderRightColor()).HasAlpha()) &&
+             (!ResolveColor(GetCSSPropertyBorderRightColor()).HasAlpha() &&
+              StyleRef().BorderRightStyle() == EBorderStyle::kSolid)) &&
             (StyleRef().BorderBottomWidth() == 0 ||
-             !ResolveColor(GetCSSPropertyBorderBottomColor()).HasAlpha())) {
+             (!ResolveColor(GetCSSPropertyBorderBottomColor()).HasAlpha() &&
+              StyleRef().BorderBottomStyle() == EBorderStyle::kSolid))) {
           continue;
         }
         // If we have an opaque background color only, we can safely paint it
@@ -268,7 +287,7 @@ void LayoutBoxModelObject::StyleDidChange(StyleDifference diff,
        (StyleRef().OriginalDisplay() == EDisplay::kInlineBlock)) &&
       ((old_style->OriginalDisplay() == EDisplay::kBlock) ||
        (old_style->OriginalDisplay() == EDisplay::kInlineBlock)))
-    Parent()->SetNeedsLayout(LayoutInvalidationReason::kChildChanged,
+    Parent()->SetNeedsLayout(layout_invalidation_reason::kChildChanged,
                              kMarkContainerChain);
 
   PaintLayerType type = LayerTypeRequired();
@@ -298,7 +317,7 @@ void LayoutBoxModelObject::StyleDidChange(StyleDifference diff,
       SetChildNeedsLayout();
     if (had_transform_related_property) {
       SetNeedsLayoutAndPrefWidthsRecalcAndFullPaintInvalidation(
-          LayoutInvalidationReason::kStyleChange);
+          layout_invalidation_reason::kStyleChange);
     }
     if (!NeedsLayout()) {
       // FIXME: We should call a specialized version of this function.
@@ -349,22 +368,21 @@ void LayoutBoxModelObject::StyleDidChange(StyleDifference diff,
   }
 
   // The used style for body background may change due to computed style change
-  // on the document element because of background stealing.
-  // Refer to backgroundStolenForBeingBody() and
-  // http://www.w3.org/TR/css3-background/#body-background for more info.
+  // on the document element because of change of BackgroundTransfersToView()
+  // which depends on the document element style.
   if (IsDocumentElement()) {
-    HTMLBodyElement* body = GetDocument().FirstBodyElement();
-    LayoutObject* body_layout = body ? body->GetLayoutObject() : nullptr;
-    if (body_layout && body_layout->IsBoxModelObject()) {
-      bool new_stole_body_background =
-          ToLayoutBoxModelObject(body_layout)
-              ->BackgroundStolenForBeingBody(Style());
-      bool old_stole_body_background =
-          old_style && ToLayoutBoxModelObject(body_layout)
-                           ->BackgroundStolenForBeingBody(old_style);
-      if (new_stole_body_background != old_stole_body_background &&
-          body_layout->Style() && body_layout->StyleRef().HasBackground()) {
-        body_layout->SetShouldDoFullPaintInvalidation();
+    if (HTMLBodyElement* body = GetDocument().FirstBodyElement()) {
+      if (auto* body_object = body->GetLayoutObject()) {
+        if (body_object->IsBoxModelObject()) {
+          auto* body_box_model = ToLayoutBoxModelObject(body_object);
+          bool new_body_background_transfers =
+              body_box_model->BackgroundTransfersToView(Style());
+          bool old_body_background_transfers =
+              old_style && body_box_model->BackgroundTransfersToView(old_style);
+          if (new_body_background_transfers != old_body_background_transfers &&
+              body_object->Style() && body_object->StyleRef().HasBackground())
+            body_object->SetBackgroundNeedsFullPaintInvalidation();
+        }
       }
     }
   }
@@ -1453,22 +1471,28 @@ void LayoutBoxModelObject::MoveChildrenTo(
   }
 }
 
-bool LayoutBoxModelObject::BackgroundStolenForBeingBody(
-    const ComputedStyle* root_element_style) const {
+bool LayoutBoxModelObject::BackgroundTransfersToView(
+    const ComputedStyle* document_element_style) const {
+  // In our painter implementation, ViewPainter instead of the painter of the
+  // layout object of the document element paints the view background.
+  if (IsDocumentElement())
+    return true;
+
   // http://www.w3.org/TR/css3-background/#body-background
-  // If the root element is <html> with no background, and a <body> child
-  // element exists, the root element steals the first <body> child element's
-  // background.
+  // If the document element is <html> with no background, and a <body> child
+  // element exists, the <body> element's background transfers to the document
+  // element which in turn transfers to the view in our painter implementation.
   if (!IsBody())
     return false;
 
-  Element* root_element = GetDocument().documentElement();
-  if (!IsHTMLHtmlElement(root_element))
+  Element* document_element = GetDocument().documentElement();
+  if (!IsHTMLHtmlElement(document_element))
     return false;
 
-  if (!root_element_style)
-    root_element_style = root_element->EnsureComputedStyle();
-  if (root_element_style->HasBackground())
+  if (!document_element_style)
+    document_element_style = document_element->GetComputedStyle();
+  DCHECK(document_element_style);
+  if (document_element_style->HasBackground())
     return false;
 
   if (GetNode() != GetDocument().FirstBodyElement())