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diff --git a/Source/WebCore/css/parser/SizesCalcParser.cpp b/Source/WebCore/css/parser/SizesCalcParser.cpp
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+++ b/Source/WebCore/css/parser/SizesCalcParser.cpp
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+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Copyright (C) 2016 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:
+//
+//    * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//    * 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.
+//    * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "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 THE COPYRIGHT
+// OWNER 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"
+#include "SizesCalcParser.h"
+
+#include "CSSParserToken.h"
+#include "RenderView.h"
+#include "SizesAttributeParser.h"
+
+namespace WebCore {
+
+SizesCalcParser::SizesCalcParser(CSSParserTokenRange range, const Document& document)
+    : m_result(0)
+    , m_document(document)
+{
+    m_isValid = calcToReversePolishNotation(range) && calculate();
+}
+
+float SizesCalcParser::result() const
+{
+    ASSERT(m_isValid);
+    return m_result;
+}
+
+static bool operatorPriority(UChar cc, bool& highPriority)
+{
+    if (cc == '+' || cc == '-')
+        highPriority = false;
+    else if (cc == '*' || cc == '/')
+        highPriority = true;
+    else
+        return false;
+    return true;
+}
+
+bool SizesCalcParser::handleOperator(Vector<CSSParserToken>& stack, const CSSParserToken& token)
+{
+    // If the token is an operator, o1, then:
+    // while there is an operator token, o2, at the top of the stack, and
+    // either o1 is left-associative and its precedence is equal to that of o2,
+    // or o1 has precedence less than that of o2,
+    // pop o2 off the stack, onto the output queue;
+    // push o1 onto the stack.
+    bool stackOperatorPriority;
+    bool incomingOperatorPriority;
+
+    if (!operatorPriority(token.delimiter(), incomingOperatorPriority))
+        return false;
+    if (!stack.isEmpty() && stack.last().type() == DelimiterToken) {
+        if (!operatorPriority(stack.last().delimiter(), stackOperatorPriority))
+            return false;
+        if (!incomingOperatorPriority || stackOperatorPriority) {
+            appendOperator(stack.last());
+            stack.removeLast();
+        }
+    }
+    stack.append(token);
+    return true;
+}
+
+void SizesCalcParser::appendNumber(const CSSParserToken& token)
+{
+    SizesCalcValue value;
+    value.value = token.numericValue();
+    m_valueList.append(value);
+}
+
+bool SizesCalcParser::appendLength(const CSSParserToken& token)
+{
+    SizesCalcValue value;
+    double result = SizesAttributeParser::computeLength(token.numericValue(), token.unitType(), m_document);
+    value.value = result;
+    value.isLength = true;
+    m_valueList.append(value);
+    return true;
+}
+
+void SizesCalcParser::appendOperator(const CSSParserToken& token)
+{
+    SizesCalcValue value;
+    value.operation = token.delimiter();
+    m_valueList.append(value);
+}
+
+bool SizesCalcParser::calcToReversePolishNotation(CSSParserTokenRange range)
+{
+    // This method implements the shunting yard algorithm, to turn the calc syntax into a reverse polish notation.
+    // http://en.wikipedia.org/wiki/Shunting-yard_algorithm
+
+    Vector<CSSParserToken> stack;
+    while (!range.atEnd()) {
+        const CSSParserToken& token = range.consume();
+        switch (token.type()) {
+        case NumberToken:
+            appendNumber(token);
+            break;
+        case DimensionToken:
+            if (!CSSPrimitiveValue::isLength(token.unitType()) || !appendLength(token))
+                return false;
+            break;
+        case DelimiterToken:
+            if (!handleOperator(stack, token))
+                return false;
+            break;
+        case FunctionToken:
+            if (!equalIgnoringASCIICase(token.value(), "calc"))
+                return false;
+            // "calc(" is the same as "("
+            FALLTHROUGH;
+        case LeftParenthesisToken:
+            // If the token is a left parenthesis, then push it onto the stack.
+            stack.append(token);
+            break;
+        case RightParenthesisToken:
+            // If the token is a right parenthesis:
+            // Until the token at the top of the stack is a left parenthesis, pop operators off the stack onto the output queue.
+            while (!stack.isEmpty() && stack.last().type() != LeftParenthesisToken && stack.last().type() != FunctionToken) {
+                appendOperator(stack.last());
+                stack.removeLast();
+            }
+            // If the stack runs out without finding a left parenthesis, then there are mismatched parentheses.
+            if (stack.isEmpty())
+                return false;
+            // Pop the left parenthesis from the stack, but not onto the output queue.
+            stack.removeLast();
+            break;
+        case WhitespaceToken:
+        case EOFToken:
+            break;
+        case CDOToken:
+        case CDCToken:
+        case AtKeywordToken:
+        case HashToken:
+        case UrlToken:
+        case BadUrlToken:
+        case PercentageToken:
+        case IncludeMatchToken:
+        case DashMatchToken:
+        case PrefixMatchToken:
+        case SuffixMatchToken:
+        case SubstringMatchToken:
+        case ColumnToken:
+        case UnicodeRangeToken:
+        case IdentToken:
+        case CommaToken:
+        case ColonToken:
+        case SemicolonToken:
+        case LeftBraceToken:
+        case LeftBracketToken:
+        case RightBraceToken:
+        case RightBracketToken:
+        case StringToken:
+        case BadStringToken:
+            return false;
+        case CommentToken:
+            ASSERT_NOT_REACHED();
+            return false;
+        }
+    }
+
+    // When there are no more tokens to read:
+    // While there are still operator tokens in the stack:
+    while (!stack.isEmpty()) {
+        // If the operator token on the top of the stack is a parenthesis, then there are mismatched parentheses.
+        CSSParserTokenType type = stack.last().type();
+        if (type == LeftParenthesisToken || type == FunctionToken)
+            return false;
+        // Pop the operator onto the output queue.
+        appendOperator(stack.last());
+        stack.removeLast();
+    }
+    return true;
+}
+
+static bool operateOnStack(Vector<SizesCalcValue>& stack, UChar operation)
+{
+    if (stack.size() < 2)
+        return false;
+    SizesCalcValue rightOperand = stack.last();
+    stack.removeLast();
+    SizesCalcValue leftOperand = stack.last();
+    stack.removeLast();
+    bool isLength;
+    switch (operation) {
+    case '+':
+        if (rightOperand.isLength != leftOperand.isLength)
+            return false;
+        isLength = (rightOperand.isLength && leftOperand.isLength);
+        stack.append(SizesCalcValue(leftOperand.value + rightOperand.value, isLength));
+        break;
+    case '-':
+        if (rightOperand.isLength != leftOperand.isLength)
+            return false;
+        isLength = (rightOperand.isLength && leftOperand.isLength);
+        stack.append(SizesCalcValue(leftOperand.value - rightOperand.value, isLength));
+        break;
+    case '*':
+        if (rightOperand.isLength && leftOperand.isLength)
+            return false;
+        isLength = (rightOperand.isLength || leftOperand.isLength);
+        stack.append(SizesCalcValue(leftOperand.value * rightOperand.value, isLength));
+        break;
+    case '/':
+        if (rightOperand.isLength || !rightOperand.value)
+            return false;
+        stack.append(SizesCalcValue(leftOperand.value / rightOperand.value, leftOperand.isLength));
+        break;
+    default:
+        return false;
+    }
+    return true;
+}
+
+bool SizesCalcParser::calculate()
+{
+    Vector<SizesCalcValue> stack;
+    for (const auto& value : m_valueList) {
+        if (!value.operation)
+            stack.append(value);
+        else {
+            if (!operateOnStack(stack, value.operation))
+                return false;
+        }
+    }
+    if (stack.size() == 1 && stack.last().isLength) {
+        m_result = std::max(clampTo<float>(stack.last().value), (float)0.0);
+        return true;
+    }
+    return false;
+}
+
+} // namespace WebCore