Pull up a subset of CanvasRenderingContext2D into BaseRenderingContext2D.

third_party/WebKit/Source/modules/canvas2d/BaseRenderingContext2D.cpp

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "modules/canvas2d/BaseRenderingContext2D.h"
+
+#include "core/css/parser/CSSParser.h"
+#include "core/frame/ImageBitmap.h"
+#include "core/html/HTMLCanvasElement.h"
+#include "core/html/HTMLImageElement.h"
+#include "core/html/HTMLVideoElement.h"
+#include "modules/canvas2d/CanvasGradient.h"
+#include "modules/canvas2d/CanvasPattern.h"
+#include "modules/canvas2d/CanvasStyle.h"
+#include "modules/canvas2d/Path2D.h"
+#include "platform/geometry/FloatQuad.h"
+#include "platform/graphics/Color.h"
+#include "platform/graphics/ExpensiveCanvasHeuristicParameters.h"
+#include "platform/graphics/Image.h"
+#include "platform/graphics/ImageBuffer.h"
+#include "platform/graphics/StrokeData.h"
+#include "platform/graphics/skia/SkiaUtils.h"
+#include "third_party/skia/include/core/SkImageFilter.h"
+
+namespace blink {
+
+static const double cDeviceScaleFactor = 1.0; // Canvas is device independent
+
+BaseRenderingContext2D::BaseRenderingContext2D()
+    : m_clipAntialiasing(NotAntiAliased)
+{
+    m_stateStack.append(CanvasRenderingContext2DState::create());
+}
+
+BaseRenderingContext2D::~BaseRenderingContext2D()
+{
+}
+
+CanvasRenderingContext2DState& BaseRenderingContext2D::modifiableState()
+{
+    realizeSaves();
+    return *m_stateStack.last();
+}
+
+void BaseRenderingContext2D::realizeSaves()
+{
+    validateStateStack();
+    if (state().hasUnrealizedSaves()) {
+        ASSERT(m_stateStack.size() >= 1);
+        // Reduce the current state's unrealized count by one now,
+        // to reflect the fact we are saving one state.
+        m_stateStack.last()->restore();
+        m_stateStack.append(CanvasRenderingContext2DState::create(state(), CanvasRenderingContext2DState::DontCopyClipList));
+        // Set the new state's unrealized count to 0, because it has no outstanding saves.
+        // We need to do this explicitly because the copy constructor and operator= used
+        // by the Vector operations copy the unrealized count from the previous state (in
+        // turn necessary to support correct resizing and unwinding of the stack).
+        m_stateStack.last()->resetUnrealizedSaveCount();
+        SkCanvas* canvas = drawingCanvas();
+        if (canvas)
+            canvas->save();
+        validateStateStack();
+    }
+}
+
+void BaseRenderingContext2D::save()
+{
+    m_stateStack.last()->save();
+}
+
+void BaseRenderingContext2D::restore()
+{
+    validateStateStack();
+    if (state().hasUnrealizedSaves()) {
+        // We never realized the save, so just record that it was unnecessary.
+        m_stateStack.last()->restore();
+        return;
+    }
+    ASSERT(m_stateStack.size() >= 1);
+    if (m_stateStack.size() <= 1)
+        return;
+    m_path.transform(state().transform());
+    m_stateStack.removeLast();
+    m_stateStack.last()->clearResolvedFilter();
+    m_path.transform(state().transform().inverse());
+    SkCanvas* c = drawingCanvas();
+    if (c)
+        c->restore();
+
+    validateStateStack();
+}
+
+static inline void convertCanvasStyleToUnionType(CanvasStyle* style, StringOrCanvasGradientOrCanvasPattern& returnValue)
+{
+    if (CanvasGradient* gradient = style->canvasGradient()) {
+        returnValue.setCanvasGradient(gradient);
+        return;
+    }
+    if (CanvasPattern* pattern = style->canvasPattern()) {
+        returnValue.setCanvasPattern(pattern);
+        return;
+    }
+    returnValue.setString(style->color());
+}
+
+void BaseRenderingContext2D::strokeStyle(StringOrCanvasGradientOrCanvasPattern& returnValue) const
+{
+    convertCanvasStyleToUnionType(state().strokeStyle(), returnValue);
+}
+
+void BaseRenderingContext2D::setStrokeStyle(const StringOrCanvasGradientOrCanvasPattern& style)
+{
+    ASSERT(!style.isNull());
+
+    String colorString;
+    CanvasStyle* canvasStyle = nullptr;
+    if (style.isString()) {
+        colorString = style.getAsString();
+        if (colorString == state().unparsedStrokeColor())
+            return;
+        Color parsedColor = 0;
+        if (!parseColorOrCurrentColor(parsedColor, colorString))
+            return;
+        if (state().strokeStyle()->isEquivalentRGBA(parsedColor.rgb())) {
+            modifiableState().setUnparsedStrokeColor(colorString);
+            return;
+        }
+        canvasStyle = CanvasStyle::createFromRGBA(parsedColor.rgb());
+    } else if (style.isCanvasGradient()) {
+        canvasStyle = CanvasStyle::createFromGradient(style.getAsCanvasGradient());
+    } else if (style.isCanvasPattern()) {
+        CanvasPattern* canvasPattern = style.getAsCanvasPattern();
+
+        if (originClean() && !canvasPattern->originClean())
+            setOriginTainted();
+
+        canvasStyle = CanvasStyle::createFromPattern(canvasPattern);
+    }
+
+    ASSERT(canvasStyle);
+
+    modifiableState().setStrokeStyle(canvasStyle);
+    modifiableState().setUnparsedStrokeColor(colorString);
+}
+
+void BaseRenderingContext2D::fillStyle(StringOrCanvasGradientOrCanvasPattern& returnValue) const
+{
+    convertCanvasStyleToUnionType(state().fillStyle(), returnValue);
+}
+
+void BaseRenderingContext2D::setFillStyle(const StringOrCanvasGradientOrCanvasPattern& style)
+{
+    ASSERT(!style.isNull());
+    validateStateStack();
+    String colorString;
+    CanvasStyle* canvasStyle = nullptr;
+    if (style.isString()) {
+        colorString = style.getAsString();
+        if (colorString == state().unparsedFillColor())
+            return;
+        Color parsedColor = 0;
+        if (!parseColorOrCurrentColor(parsedColor, colorString))
+            return;
+        if (state().fillStyle()->isEquivalentRGBA(parsedColor.rgb())) {
+            modifiableState().setUnparsedFillColor(colorString);
+            return;
+        }
+        canvasStyle = CanvasStyle::createFromRGBA(parsedColor.rgb());
+    } else if (style.isCanvasGradient()) {
+        canvasStyle = CanvasStyle::createFromGradient(style.getAsCanvasGradient());
+    } else if (style.isCanvasPattern()) {
+        CanvasPattern* canvasPattern = style.getAsCanvasPattern();
+
+        if (originClean() && !canvasPattern->originClean())
+            setOriginTainted();
+        if (canvasPattern->pattern()->isTextureBacked())
+            disableDeferral(DisableDeferralReasonUsingTextureBackedPattern);
+        canvasStyle = CanvasStyle::createFromPattern(canvasPattern);
+    }
+
+    ASSERT(canvasStyle);
+    modifiableState().setFillStyle(canvasStyle);
+    modifiableState().setUnparsedFillColor(colorString);
+}
+
+double BaseRenderingContext2D::lineWidth() const
+{
+    return state().lineWidth();
+}
+
+void BaseRenderingContext2D::setLineWidth(double width)
+{
+    if (!std::isfinite(width) || width <= 0)
+        return;
+    if (state().lineWidth() == width)
+        return;
+    modifiableState().setLineWidth(width);
+}
+
+String BaseRenderingContext2D::lineCap() const
+{
+    return lineCapName(state().lineCap());
+}
+
+void BaseRenderingContext2D::setLineCap(const String& s)
+{
+    LineCap cap;
+    if (!parseLineCap(s, cap))
+        return;
+    if (state().lineCap() == cap)
+        return;
+    modifiableState().setLineCap(cap);
+}
+
+String BaseRenderingContext2D::lineJoin() const
+{
+    return lineJoinName(state().lineJoin());
+}
+
+void BaseRenderingContext2D::setLineJoin(const String& s)
+{
+    LineJoin join;
+    if (!parseLineJoin(s, join))
+        return;
+    if (state().lineJoin() == join)
+        return;
+    modifiableState().setLineJoin(join);
+}
+
+double BaseRenderingContext2D::miterLimit() const
+{
+    return state().miterLimit();
+}
+
+void BaseRenderingContext2D::setMiterLimit(double limit)
+{
+    if (!std::isfinite(limit) || limit <= 0)
+        return;
+    if (state().miterLimit() == limit)
+        return;
+    modifiableState().setMiterLimit(limit);
+}
+
+double BaseRenderingContext2D::shadowOffsetX() const
+{
+    return state().shadowOffset().width();
+}
+
+void BaseRenderingContext2D::setShadowOffsetX(double x)
+{
+    if (!std::isfinite(x))
+        return;
+    if (state().shadowOffset().width() == x)
+        return;
+    modifiableState().setShadowOffsetX(x);
+}
+
+double BaseRenderingContext2D::shadowOffsetY() const
+{
+    return state().shadowOffset().height();
+}
+
+void BaseRenderingContext2D::setShadowOffsetY(double y)
+{
+    if (!std::isfinite(y))
+        return;
+    if (state().shadowOffset().height() == y)
+        return;
+    modifiableState().setShadowOffsetY(y);
+}
+
+double BaseRenderingContext2D::shadowBlur() const
+{
+    return state().shadowBlur();
+}
+
+void BaseRenderingContext2D::setShadowBlur(double blur)
+{
+    if (!std::isfinite(blur) || blur < 0)
+        return;
+    if (state().shadowBlur() == blur)
+        return;
+    modifiableState().setShadowBlur(blur);
+}
+
+String BaseRenderingContext2D::shadowColor() const
+{
+    return Color(state().shadowColor()).serialized();
+}
+
+void BaseRenderingContext2D::setShadowColor(const String& colorString)
+{
+    Color color;
+    if (!parseColorOrCurrentColor(color, colorString))
+        return;
+    if (state().shadowColor() == color)
+        return;
+    modifiableState().setShadowColor(color.rgb());
+}
+
+const Vector<double>& BaseRenderingContext2D::getLineDash() const
+{
+    return state().lineDash();
+}
+
+static bool lineDashSequenceIsValid(const Vector<double>& dash)
+{
+    for (size_t i = 0; i < dash.size(); i++) {
+        if (!std::isfinite(dash[i]) || dash[i] < 0)
+            return false;
+    }
+    return true;
+}
+
+void BaseRenderingContext2D::setLineDash(const Vector<double>& dash)
+{
+    if (!lineDashSequenceIsValid(dash))
+        return;
+    modifiableState().setLineDash(dash);
+}
+
+double BaseRenderingContext2D::lineDashOffset() const
+{
+    return state().lineDashOffset();
+}
+
+void BaseRenderingContext2D::setLineDashOffset(double offset)
+{
+    if (!std::isfinite(offset) || state().lineDashOffset() == offset)
+        return;
+    modifiableState().setLineDashOffset(offset);
+}
+
+double BaseRenderingContext2D::globalAlpha() const
+{
+    return state().globalAlpha();
+}
+
+void BaseRenderingContext2D::setGlobalAlpha(double alpha)
+{
+    if (!(alpha >= 0 && alpha <= 1))
+        return;
+    if (state().globalAlpha() == alpha)
+        return;
+    modifiableState().setGlobalAlpha(alpha);
+}
+
+String BaseRenderingContext2D::globalCompositeOperation() const
+{
+    return compositeOperatorName(compositeOperatorFromSkia(state().globalComposite()), blendModeFromSkia(state().globalComposite()));
+}
+
+void BaseRenderingContext2D::setGlobalCompositeOperation(const String& operation)
+{
+    CompositeOperator op = CompositeSourceOver;
+    WebBlendMode blendMode = WebBlendModeNormal;
+    if (!parseCompositeAndBlendOperator(operation, op, blendMode))
+        return;
+    SkXfermode::Mode xfermode = WebCoreCompositeToSkiaComposite(op, blendMode);
+    if (state().globalComposite() == xfermode)
+        return;
+    modifiableState().setGlobalComposite(xfermode);
+}
+
+String BaseRenderingContext2D::filter() const
+{
+    return state().unparsedFilter();
+}
+
+void BaseRenderingContext2D::setFilter(const String& filterString)
+{
+    if (filterString == state().unparsedFilter())
+        return;
+
+    RefPtrWillBeRawPtr<CSSValue> filterValue = CSSParser::parseSingleValue(CSSPropertyWebkitFilter, filterString, CSSParserContext(HTMLStandardMode, 0));
+
+    if (!filterValue || filterValue->isInitialValue() || filterValue->isInheritedValue())
+        return;
+
+    modifiableState().setUnparsedFilter(filterString);
+    modifiableState().setFilter(filterValue.release());
+}
+
+PassRefPtrWillBeRawPtr<SVGMatrixTearOff> BaseRenderingContext2D::currentTransform() const
+{
+    return SVGMatrixTearOff::create(state().transform());
+}
+
+void BaseRenderingContext2D::setCurrentTransform(PassRefPtrWillBeRawPtr<SVGMatrixTearOff> passMatrixTearOff)
+{
+    RefPtrWillBeRawPtr<SVGMatrixTearOff> matrixTearOff = passMatrixTearOff;
+    const AffineTransform& transform = matrixTearOff->value();
+    setTransform(transform.a(), transform.b(), transform.c(), transform.d(), transform.e(), transform.f());
+}
+
+void BaseRenderingContext2D::scale(double sx, double sy)
+{
+    SkCanvas* c = drawingCanvas();
+    if (!c)
+        return;
+
+    if (!std::isfinite(sx) || !std::isfinite(sy))
+        return;
+
+    AffineTransform newTransform = state().transform();
+    newTransform.scaleNonUniform(sx, sy);
+    if (state().transform() == newTransform)
+        return;
+
+    modifiableState().setTransform(newTransform);
+    if (!state().isTransformInvertible())
+        return;
+
+    c->scale(sx, sy);
+    m_path.transform(AffineTransform().scaleNonUniform(1.0 / sx, 1.0 / sy));
+}
+
+void BaseRenderingContext2D::rotate(double angleInRadians)
+{
+    SkCanvas* c = drawingCanvas();
+    if (!c)
+        return;
+
+    if (!std::isfinite(angleInRadians))
+        return;
+
+    AffineTransform newTransform = state().transform();
+    newTransform.rotateRadians(angleInRadians);
+    if (state().transform() == newTransform)
+        return;
+
+    modifiableState().setTransform(newTransform);
+    if (!state().isTransformInvertible())
+        return;
+    c->rotate(angleInRadians * (180.0 / piFloat));
+    m_path.transform(AffineTransform().rotateRadians(-angleInRadians));
+}
+
+void BaseRenderingContext2D::translate(double tx, double ty)
+{
+    SkCanvas* c = drawingCanvas();
+    if (!c)
+        return;
+    if (!state().isTransformInvertible())
+        return;
+
+    if (!std::isfinite(tx) || !std::isfinite(ty))
+        return;
+
+    AffineTransform newTransform = state().transform();
+    newTransform.translate(tx, ty);
+    if (state().transform() == newTransform)
+        return;
+
+    modifiableState().setTransform(newTransform);
+    if (!state().isTransformInvertible())
+        return;
+    c->translate(tx, ty);
+    m_path.transform(AffineTransform().translate(-tx, -ty));
+}
+
+void BaseRenderingContext2D::transform(double m11, double m12, double m21, double m22, double dx, double dy)
+{
+    SkCanvas* c = drawingCanvas();
+    if (!c)
+        return;
+
+    if (!std::isfinite(m11) || !std::isfinite(m21) || !std::isfinite(dx) || !std::isfinite(m12) || !std::isfinite(m22) || !std::isfinite(dy))
+        return;
+
+    AffineTransform transform(m11, m12, m21, m22, dx, dy);
+    AffineTransform newTransform = state().transform() * transform;
+    if (state().transform() == newTransform)
+        return;
+
+    modifiableState().setTransform(newTransform);
+    if (!state().isTransformInvertible())
+        return;
+
+    c->concat(affineTransformToSkMatrix(transform));
+    m_path.transform(transform.inverse());
+}
+
+void BaseRenderingContext2D::resetTransform()
+{
+    SkCanvas* c = drawingCanvas();
+    if (!c)
+        return;
+
+    AffineTransform ctm = state().transform();
+    bool invertibleCTM = state().isTransformInvertible();
+    // It is possible that CTM is identity while CTM is not invertible.
+    // When CTM becomes non-invertible, realizeSaves() can make CTM identity.
+    if (ctm.isIdentity() && invertibleCTM)
+        return;
+
+    // resetTransform() resolves the non-invertible CTM state.
+    modifiableState().resetTransform();
+    c->setMatrix(affineTransformToSkMatrix(baseTransform()));
+
+    if (invertibleCTM)
+        m_path.transform(ctm);
+    // When else, do nothing because all transform methods didn't update m_path when CTM became non-invertible.
+    // It means that resetTransform() restores m_path just before CTM became non-invertible.
+}
+
+void BaseRenderingContext2D::setTransform(double m11, double m12, double m21, double m22, double dx, double dy)
+{
+    SkCanvas* c = drawingCanvas();
+    if (!c)
+        return;
+
+    if (!std::isfinite(m11) || !std::isfinite(m21) || !std::isfinite(dx) || !std::isfinite(m12) || !std::isfinite(m22) || !std::isfinite(dy))
+        return;
+
+    resetTransform();
+    transform(m11, m12, m21, m22, dx, dy);
+}
+
+void BaseRenderingContext2D::beginPath()
+{
+    m_path.clear();
+}
+
+static bool validateRectForCanvas(double& x, double& y, double& width, double& height)
+{
+    if (!std::isfinite(x) || !std::isfinite(y) || !std::isfinite(width) || !std::isfinite(height))
+        return false;
+
+    if (!width && !height)
+        return false;
+
+    if (width < 0) {
+        width = -width;
+        x -= width;
+    }
+
+    if (height < 0) {
+        height = -height;
+        y -= height;
+    }
+
+    return true;
+}
+
+void BaseRenderingContext2D::drawForText(const Font& font, const TextRunPaintInfo& textRunPaintInfo, const FloatPoint& location, CanvasRenderingContext2DState::PaintType paintType)
+{
+    draw(
+        [&font, this, &textRunPaintInfo, &location](SkCanvas* c, const SkPaint* paint) // draw lambda
+        {
+            font.drawBidiText(c, textRunPaintInfo, location, Font::UseFallbackIfFontNotReady, cDeviceScaleFactor, *paint);
+        },
+        [](const SkIRect& rect) // overdraw test lambda
+        {
+            return false;
+        },
+        textRunPaintInfo.bounds, paintType);
+}
+
+static bool isFullCanvasCompositeMode(SkXfermode::Mode op)
+{
+    // See 4.8.11.1.3 Compositing
+    // CompositeSourceAtop and CompositeDestinationOut are not listed here as the platforms already
+    // implement the specification's behavior.
+    return op == SkXfermode::kSrcIn_Mode || op == SkXfermode::kSrcOut_Mode || op == SkXfermode::kDstIn_Mode || op == SkXfermode::kDstATop_Mode;
+}
+
+template<typename DrawFunc>
+void BaseRenderingContext2D::compositedDraw(const DrawFunc& drawFunc, SkCanvas* c, CanvasRenderingContext2DState::PaintType paintType, CanvasRenderingContext2DState::ImageType imageType)
+{
+    SkImageFilter* filter = stateGetFilter();
+    ASSERT(isFullCanvasCompositeMode(state().globalComposite()) || filter);
+    SkMatrix ctm = c->getTotalMatrix();
+    c->resetMatrix();
+    SkPaint compositePaint;
+    compositePaint.setXfermodeMode(state().globalComposite());
+    if (state().shouldDrawShadows()) {
+        // unroll into two independently composited passes if drawing shadows
+        SkPaint shadowPaint = *state().getPaint(paintType, DrawShadowOnly, imageType);
+        int saveCount = c->getSaveCount();
+        if (filter) {
+            SkPaint filterPaint;
+            filterPaint.setImageFilter(filter);
+            // TODO(junov): crbug.com/502921 We could use primitive bounds if we knew that the filter
+            // does not affect transparent black regions.
+            c->saveLayer(nullptr, &shadowPaint);
+            c->saveLayer(nullptr, &filterPaint);
+            SkPaint foregroundPaint = *state().getPaint(paintType, DrawForegroundOnly, imageType);
+            c->setMatrix(ctm);
+            drawFunc(c, &foregroundPaint);
+        } else {
+            ASSERT(isFullCanvasCompositeMode(state().globalComposite()));
+            c->saveLayer(nullptr, &compositePaint);
+            shadowPaint.setXfermodeMode(SkXfermode::kSrcOver_Mode);
+            c->setMatrix(ctm);
+            drawFunc(c, &shadowPaint);
+        }
+        c->restoreToCount(saveCount);
+    }
+
+    compositePaint.setImageFilter(filter);
+    // TODO(junov): crbug.com/502921 We could use primitive bounds if we knew that the filter
+    // does not affect transparent black regions *and* !isFullCanvasCompositeMode
+    c->saveLayer(nullptr, &compositePaint);
+    SkPaint foregroundPaint = *state().getPaint(paintType, DrawForegroundOnly, imageType);
+    foregroundPaint.setXfermodeMode(SkXfermode::kSrcOver_Mode);
+    c->setMatrix(ctm);
+    drawFunc(c, &foregroundPaint);
+    c->restore();
+    c->setMatrix(ctm);
+}
+
+template<typename DrawFunc, typename ContainsFunc>
+bool BaseRenderingContext2D::draw(const DrawFunc& drawFunc, const ContainsFunc& drawCoversClipBounds, const SkRect& bounds, CanvasRenderingContext2DState::PaintType paintType, CanvasRenderingContext2DState::ImageType imageType)
+{
+    if (!state().isTransformInvertible())
+        return false;
+
+    SkIRect clipBounds;
+    if (!drawingCanvas() || !drawingCanvas()->getClipDeviceBounds(&clipBounds))
+        return false;
+
+    // If gradient size is zero, then paint nothing.
+    CanvasStyle* style = state().style(paintType);
+    if (style) {
+        CanvasGradient* gradient = style->canvasGradient();
+        if (gradient && gradient->gradient()->isZeroSize())
+            return false;
+    }
+
+    if (isFullCanvasCompositeMode(state().globalComposite()) || stateHasFilter()) {
+        compositedDraw(drawFunc, drawingCanvas(), paintType, imageType);
+        didDraw(clipBounds);
+    } else if (state().globalComposite() == SkXfermode::kSrc_Mode) {
+        clearCanvas(); // takes care of checkOverdraw()
+        const SkPaint* paint = state().getPaint(paintType, DrawForegroundOnly, imageType);
+        drawFunc(drawingCanvas(), paint);
+        didDraw(clipBounds);
+    } else {
+        SkIRect dirtyRect;
+        if (computeDirtyRect(bounds, clipBounds, &dirtyRect)) {
+            const SkPaint* paint = state().getPaint(paintType, DrawShadowAndForeground, imageType);
+            if (paintType != CanvasRenderingContext2DState::StrokePaintType && drawCoversClipBounds(clipBounds))
+                checkOverdraw(bounds, paint, imageType, ClipFill);
+            drawFunc(drawingCanvas(), paint);
+            didDraw(dirtyRect);
+        }
+    }
+    return true;
+}
+
+static bool isPathExpensive(const Path& path)
+{
+    const SkPath& skPath = path.skPath();
+    if (ExpensiveCanvasHeuristicParameters::ConcavePathsAreExpensive && !skPath.isConvex())
+        return true;
+
+    if (skPath.countPoints() > ExpensiveCanvasHeuristicParameters::ExpensivePathPointCount)
+        return true;
+
+    return false;
+}
+
+void BaseRenderingContext2D::drawPathInternal(const Path& path, CanvasRenderingContext2DState::PaintType paintType, SkPath::FillType fillType)
+{
+    if (path.isEmpty())
+        return;
+
+    SkPath skPath = path.skPath();
+    FloatRect bounds = path.boundingRect();
+    skPath.setFillType(fillType);
+
+    if (paintType == CanvasRenderingContext2DState::StrokePaintType)
+        inflateStrokeRect(bounds);
+
+    if (!drawingCanvas())
+        return;
+
+    if (draw(
+        [&skPath, this](SkCanvas* c, const SkPaint* paint) // draw lambda
+        {
+            c->drawPath(skPath, *paint);
+        },
+        [](const SkIRect& rect) // overdraw test lambda
+        {
+            return false;
+        }, bounds, paintType)) {
+        if (isPathExpensive(path)) {
+            ImageBuffer* buffer = imageBuffer();
+            if (buffer)
+                buffer->setHasExpensiveOp();
+        }
+    }
+}
+
+static SkPath::FillType parseWinding(const String& windingRuleString)
+{
+    if (windingRuleString == "nonzero")
+        return SkPath::kWinding_FillType;
+    if (windingRuleString == "evenodd")
+        return SkPath::kEvenOdd_FillType;
+
+    ASSERT_NOT_REACHED();
+    return SkPath::kEvenOdd_FillType;
+}
+
+void BaseRenderingContext2D::fill(const String& windingRuleString)
+{
+    drawPathInternal(m_path, CanvasRenderingContext2DState::FillPaintType, parseWinding(windingRuleString));
+}
+
+void BaseRenderingContext2D::fill(Path2D* domPath, const String& windingRuleString)
+{
+    drawPathInternal(domPath->path(), CanvasRenderingContext2DState::FillPaintType, parseWinding(windingRuleString));
+}
+
+void BaseRenderingContext2D::stroke()
+{
+    drawPathInternal(m_path, CanvasRenderingContext2DState::StrokePaintType);
+}
+
+void BaseRenderingContext2D::stroke(Path2D* domPath)
+{
+    drawPathInternal(domPath->path(), CanvasRenderingContext2DState::StrokePaintType);
+}
+
+void BaseRenderingContext2D::fillRect(double x, double y, double width, double height)
+{
+    if (!validateRectForCanvas(x, y, width, height))
+        return;
+
+    if (!drawingCanvas())
+        return;
+
+    SkRect rect = SkRect::MakeXYWH(x, y, width, height);
+    draw(
+        [&rect, this](SkCanvas* c, const SkPaint* paint) // draw lambda
+        {
+            c->drawRect(rect, *paint);
+        },
+        [&rect, this](const SkIRect& clipBounds) // overdraw test lambda
+        {
+            return rectContainsTransformedRect(rect, clipBounds);
+        }, rect, CanvasRenderingContext2DState::FillPaintType);
+}
+
+static void strokeRectOnCanvas(const FloatRect& rect, SkCanvas* canvas, const SkPaint* paint)
+{
+    ASSERT(paint->getStyle() == SkPaint::kStroke_Style);
+    if ((rect.width() > 0) != (rect.height() > 0)) {
+        // When stroking, we must skip the zero-dimension segments
+        SkPath path;
+        path.moveTo(rect.x(), rect.y());
+        path.lineTo(rect.maxX(), rect.maxY());
+        path.close();
+        canvas->drawPath(path, *paint);
+        return;
+    }
+    canvas->drawRect(rect, *paint);
+}
+
+void BaseRenderingContext2D::strokeRect(double x, double y, double width, double height)
+{
+    if (!validateRectForCanvas(x, y, width, height))
+        return;
+
+    if (!drawingCanvas())
+        return;
+
+    SkRect rect = SkRect::MakeXYWH(x, y, width, height);
+    FloatRect bounds = rect;
+    inflateStrokeRect(bounds);
+    draw(
+        [&rect, this](SkCanvas* c, const SkPaint* paint) // draw lambda
+        {
+            strokeRectOnCanvas(rect, c, paint);
+        },
+        [](const SkIRect& clipBounds) // overdraw test lambda
+        {
+            return false;
+        }, bounds, CanvasRenderingContext2DState::StrokePaintType);
+}
+
+void BaseRenderingContext2D::clipInternal(const Path& path, const String& windingRuleString)
+{
+    SkCanvas* c = drawingCanvas();
+    if (!c) {
+        return;
+    }
+    if (!state().isTransformInvertible()) {
+        return;
+    }
+
+    SkPath skPath = path.skPath();
+    skPath.setFillType(parseWinding(windingRuleString));
+    modifiableState().clipPath(skPath, m_clipAntialiasing);
+    c->clipPath(skPath, SkRegion::kIntersect_Op, m_clipAntialiasing == AntiAliased);
+    if (ExpensiveCanvasHeuristicParameters::ComplexClipsAreExpensive && !skPath.isRect(0) && hasImageBuffer()) {
+        imageBuffer()->setHasExpensiveOp();
+    }
+}
+
+void BaseRenderingContext2D::clip(const String& windingRuleString)
+{
+    clipInternal(m_path, windingRuleString);
+}
+
+void BaseRenderingContext2D::clip(Path2D* domPath, const String& windingRuleString)
+{
+    clipInternal(domPath->path(), windingRuleString);
+}
+
+bool BaseRenderingContext2D::isPointInPath(const double x, const double y, const String& windingRuleString)
+{
+    return isPointInPathInternal(m_path, x, y, windingRuleString);
+}
+
+bool BaseRenderingContext2D::isPointInPath(Path2D* domPath, const double x, const double y, const String& windingRuleString)
+{
+    return isPointInPathInternal(domPath->path(), x, y, windingRuleString);
+}
+
+bool BaseRenderingContext2D::isPointInPathInternal(const Path& path, const double x, const double y, const String& windingRuleString)
+{
+    SkCanvas* c = drawingCanvas();
+    if (!c)
+        return false;
+    if (!state().isTransformInvertible())
+        return false;
+
+    FloatPoint point(x, y);
+    if (!std::isfinite(point.x()) || !std::isfinite(point.y()))
+        return false;
+    AffineTransform ctm = state().transform();
+    FloatPoint transformedPoint = ctm.inverse().mapPoint(point);
+
+    return path.contains(transformedPoint, SkFillTypeToWindRule(parseWinding(windingRuleString)));
+}
+
+bool BaseRenderingContext2D::isPointInStroke(const double x, const double y)
+{
+    return isPointInStrokeInternal(m_path, x, y);
+}
+
+bool BaseRenderingContext2D::isPointInStroke(Path2D* domPath, const double x, const double y)
+{
+    return isPointInStrokeInternal(domPath->path(), x, y);
+}
+
+bool BaseRenderingContext2D::isPointInStrokeInternal(const Path& path, const double x, const double y)
+{
+    SkCanvas* c = drawingCanvas();
+    if (!c)
+        return false;
+    if (!state().isTransformInvertible())
+        return false;
+
+    FloatPoint point(x, y);
+    if (!std::isfinite(point.x()) || !std::isfinite(point.y()))
+        return false;
+    AffineTransform ctm = state().transform();
+    FloatPoint transformedPoint = ctm.inverse().mapPoint(point);
+
+    StrokeData strokeData;
+    strokeData.setThickness(state().lineWidth());
+    strokeData.setLineCap(state().lineCap());
+    strokeData.setLineJoin(state().lineJoin());
+    strokeData.setMiterLimit(state().miterLimit());
+    Vector<float> lineDash(state().lineDash().size());
+    std::copy(state().lineDash().begin(), state().lineDash().end(), lineDash.begin());
+    strokeData.setLineDash(lineDash, state().lineDashOffset());
+    return path.strokeContains(transformedPoint, strokeData);
+}
+
+void BaseRenderingContext2D::clearRect(double x, double y, double width, double height)
+{
+    if (!validateRectForCanvas(x, y, width, height))
+        return;
+
+    SkCanvas* c = drawingCanvas();
+    if (!c)
+        return;
+    if (!state().isTransformInvertible())
+        return;
+
+    SkIRect clipBounds;
+    if (!c->getClipDeviceBounds(&clipBounds))
+        return;
+
+    SkPaint clearPaint;
+    clearPaint.setXfermodeMode(SkXfermode::kClear_Mode);
+    clearPaint.setStyle(SkPaint::kFill_Style);
+    FloatRect rect(x, y, width, height);
+
+    if (rectContainsTransformedRect(rect, clipBounds)) {
+        checkOverdraw(rect, &clearPaint, CanvasRenderingContext2DState::NoImage, ClipFill);
+        if (drawingCanvas())
+            drawingCanvas()->drawRect(rect, clearPaint);
+        didDraw(clipBounds);
+    } else {
+        SkIRect dirtyRect;
+        if (computeDirtyRect(rect, clipBounds, &dirtyRect)) {
+            c->drawRect(rect, clearPaint);
+            didDraw(dirtyRect);
+        }
+    }
+}
+
+static inline FloatRect normalizeRect(const FloatRect& rect)
+{
+    return FloatRect(std::min(rect.x(), rect.maxX()),
+        std::min(rect.y(), rect.maxY()),
+        std::max(rect.width(), -rect.width()),
+        std::max(rect.height(), -rect.height()));
+}
+
+static inline void clipRectsToImageRect(const FloatRect& imageRect, FloatRect* srcRect, FloatRect* dstRect)
+{
+    if (imageRect.contains(*srcRect))
+        return;
+
+    // Compute the src to dst transform
+    FloatSize scale(dstRect->size().width() / srcRect->size().width(), dstRect->size().height() / srcRect->size().height());
+    FloatPoint scaledSrcLocation = srcRect->location();
+    scaledSrcLocation.scale(scale.width(), scale.height());
+    FloatSize offset = dstRect->location() - scaledSrcLocation;
+
+    srcRect->intersect(imageRect);
+
+    // To clip the destination rectangle in the same proportion, transform the clipped src rect
+    *dstRect = *srcRect;
+    dstRect->scale(scale.width(), scale.height());
+    dstRect->move(offset);
+}
+
+static inline CanvasImageSource* toImageSourceInternal(const CanvasImageSourceUnion& value)
+{
+    if (value.isHTMLImageElement())
+        return value.getAsHTMLImageElement().get();
+    if (value.isHTMLVideoElement())
+        return value.getAsHTMLVideoElement().get();
+    if (value.isHTMLCanvasElement())
+        return value.getAsHTMLCanvasElement().get();
+    if (value.isImageBitmap())
+        return value.getAsImageBitmap().get();
+    ASSERT_NOT_REACHED();
+    return nullptr;
+}
+
+void BaseRenderingContext2D::drawImage(const CanvasImageSourceUnion& imageSource, double x, double y, ExceptionState& exceptionState)
+{
+    CanvasImageSource* imageSourceInternal = toImageSourceInternal(imageSource);
+    FloatSize sourceRectSize = imageSourceInternal->elementSize();
+    FloatSize destRectSize = imageSourceInternal->defaultDestinationSize();
+    drawImage(imageSourceInternal, 0, 0, sourceRectSize.width(), sourceRectSize.height(), x, y, destRectSize.width(), destRectSize.height(), exceptionState);
+}
+
+void BaseRenderingContext2D::drawImage(const CanvasImageSourceUnion& imageSource,
+    double x, double y, double width, double height, ExceptionState& exceptionState)
+{
+    CanvasImageSource* imageSourceInternal = toImageSourceInternal(imageSource);
+    FloatSize sourceRectSize = imageSourceInternal->elementSize();
+    drawImage(imageSourceInternal, 0, 0, sourceRectSize.width(), sourceRectSize.height(), x, y, width, height, exceptionState);
+}
+
+void BaseRenderingContext2D::drawImage(const CanvasImageSourceUnion& imageSource,
+    double sx, double sy, double sw, double sh,
+    double dx, double dy, double dw, double dh, ExceptionState& exceptionState)
+{
+    CanvasImageSource* imageSourceInternal = toImageSourceInternal(imageSource);
+    drawImage(imageSourceInternal, sx, sy, sw, sh, dx, dy, dw, dh, exceptionState);
+}
+
+bool BaseRenderingContext2D::shouldDrawImageAntialiased(const FloatRect& destRect) const
+{
+    if (!state().shouldAntialias())
+        return false;
+    SkCanvas* c = drawingCanvas();
+    ASSERT(c);
+
+    const SkMatrix &ctm = c->getTotalMatrix();
+    // Don't disable anti-aliasing if we're rotated or skewed.
+    if (!ctm.rectStaysRect())
+        return true;
+    // Check if the dimensions of the destination are "small" (less than one
+    // device pixel). To prevent sudden drop-outs. Since we know that
+    // kRectStaysRect_Mask is set, the matrix either has scale and no skew or
+    // vice versa. We can query the kAffine_Mask flag to determine which case
+    // it is.
+    // FIXME: This queries the CTM while drawing, which is generally
+    // discouraged. Always drawing with AA can negatively impact performance
+    // though - that's why it's not always on.
+    SkScalar widthExpansion, heightExpansion;
+    if (ctm.getType() & SkMatrix::kAffine_Mask)
+        widthExpansion = ctm[SkMatrix::kMSkewY], heightExpansion = ctm[SkMatrix::kMSkewX];
+    else
+        widthExpansion = ctm[SkMatrix::kMScaleX], heightExpansion = ctm[SkMatrix::kMScaleY];
+    return destRect.width() * fabs(widthExpansion) < 1 || destRect.height() * fabs(heightExpansion) < 1;
+}
+
+void BaseRenderingContext2D::drawImageInternal(SkCanvas* c, CanvasImageSource* imageSource, Image* image, const FloatRect& srcRect, const FloatRect& dstRect, const SkPaint* paint)
+{
+    int initialSaveCount = c->getSaveCount();
+    SkPaint imagePaint = *paint;
+
+    if (paint->getImageFilter()) {
+        SkMatrix invCtm;
+        if (!c->getTotalMatrix().invert(&invCtm)) {
+            // There is an earlier check for invertibility, but the arithmetic
+            // in AffineTransform is not exactly identical, so it is possible
+            // for SkMatrix to find the transform to be non-invertible at this stage.
+            // crbug.com/504687
+            return;
+        }
+        SkRect bounds = dstRect;
+        SkPaint layerPaint;
+        layerPaint.setXfermode(paint->getXfermode());
+        SkAutoTUnref<SkImageFilter> localFilter(paint->getImageFilter()->newWithLocalMatrix(invCtm));
+        layerPaint.setImageFilter(localFilter);
+        c->saveLayer(&bounds, &layerPaint);
+        imagePaint.setXfermodeMode(SkXfermode::kSrcOver_Mode);
+        imagePaint.setImageFilter(nullptr);
+    }
+
+    if (!imageSource->isVideoElement()) {
+        imagePaint.setAntiAlias(shouldDrawImageAntialiased(dstRect));
+        image->draw(c, imagePaint, dstRect, srcRect, DoNotRespectImageOrientation, Image::DoNotClampImageToSourceRect);
+    } else {
+        c->save();
+        c->clipRect(dstRect);
+        c->translate(dstRect.x(), dstRect.y());
+        c->scale(dstRect.width() / srcRect.width(), dstRect.height() / srcRect.height());
+        c->translate(-srcRect.x(), -srcRect.y());
+        HTMLVideoElement* video = static_cast<HTMLVideoElement*>(imageSource);
+        video->paintCurrentFrame(c, IntRect(IntPoint(), IntSize(video->videoWidth(), video->videoHeight())), &imagePaint);
+    }
+
+    c->restoreToCount(initialSaveCount);
+}
+
+bool shouldDisableDeferral(CanvasImageSource* imageSource, DisableDeferralReason* reason)
+{
+    ASSERT(reason);
+    ASSERT(*reason == DisableDeferralReasonUnknown);
+
+    if (imageSource->isVideoElement()) {
+        *reason = DisableDeferralReasonDrawImageOfVideo;
+        return true;
+    }
+    if (imageSource->isCanvasElement()) {
+        HTMLCanvasElement* canvas = static_cast<HTMLCanvasElement*>(imageSource);
+        if (canvas->isAnimated2D()) {
+            *reason = DisableDeferralReasonDrawImageOfAnimated2dCanvas;
+            return true;
+        }
+    }
+    return false;
+}
+
+void BaseRenderingContext2D::drawImage(CanvasImageSource* imageSource,
+    double sx, double sy, double sw, double sh,
+    double dx, double dy, double dw, double dh, ExceptionState& exceptionState)
+{
+    if (!drawingCanvas())
+        return;
+
+    RefPtr<Image> image;
+    SourceImageStatus sourceImageStatus = InvalidSourceImageStatus;
+    if (!imageSource->isVideoElement()) {
+        AccelerationHint hint = imageBuffer()->isAccelerated() ? PreferAcceleration : PreferNoAcceleration;
+        image = imageSource->getSourceImageForCanvas(&sourceImageStatus, hint, SnapshotReasonDrawImage);
+        if (sourceImageStatus == UndecodableSourceImageStatus)
+            exceptionState.throwDOMException(InvalidStateError, "The HTMLImageElement provided is in the 'broken' state.");
+        if (!image || !image->width() || !image->height())
+            return;
+    } else {
+        if (!static_cast<HTMLVideoElement*>(imageSource)->hasAvailableVideoFrame())
+            return;
+    }
+
+    if (!std::isfinite(dx) || !std::isfinite(dy) || !std::isfinite(dw) || !std::isfinite(dh)
+        || !std::isfinite(sx) || !std::isfinite(sy) || !std::isfinite(sw) || !std::isfinite(sh)
+        || !dw || !dh || !sw || !sh)
+        return;
+
+    FloatRect srcRect = normalizeRect(FloatRect(sx, sy, sw, sh));
+    FloatRect dstRect = normalizeRect(FloatRect(dx, dy, dw, dh));
+
+    clipRectsToImageRect(FloatRect(FloatPoint(), imageSource->elementSize()), &srcRect, &dstRect);
+
+    imageSource->adjustDrawRects(&srcRect, &dstRect);
+
+    if (srcRect.isEmpty())
+        return;
+
+    DisableDeferralReason reason = DisableDeferralReasonUnknown;
+    if (shouldDisableDeferral(imageSource, &reason) || image->isTextureBacked())
+        disableDeferral(reason);
+
+    validateStateStack();
+
+    draw(
+        [this, &imageSource, &image, &srcRect, dstRect](SkCanvas* c, const SkPaint* paint) // draw lambda
+        {
+            drawImageInternal(c, imageSource, image.get(), srcRect, dstRect, paint);
+        },
+        [this, &dstRect](const SkIRect& clipBounds) // overdraw test lambda
+        {
+            return rectContainsTransformedRect(dstRect, clipBounds);
+        }, dstRect, CanvasRenderingContext2DState::ImagePaintType,
+        imageSource->isOpaque() ? CanvasRenderingContext2DState::OpaqueImage : CanvasRenderingContext2DState::NonOpaqueImage);
+
+    validateStateStack();
+
+    bool isExpensive = false;
+
+    if (ExpensiveCanvasHeuristicParameters::SVGImageSourcesAreExpensive && imageSource->isSVGSource())
+        isExpensive = true;
+
+    if (imageSource->elementSize().width() * imageSource->elementSize().height() > width() * height() * ExpensiveCanvasHeuristicParameters::ExpensiveImageSizeRatio)
+        isExpensive = true;
+
+    if (isExpensive) {
+        ImageBuffer* buffer = imageBuffer();
+        if (buffer)
+            buffer->setHasExpensiveOp();
+    }
+
+    if (imageSource->isCanvasElement() && static_cast<HTMLCanvasElement*>(imageSource)->is3D()) {
+        // WebGL to 2D canvas: must flush graphics context to prevent a race
+        // FIXME: crbug.com/516331 Fix the underlying synchronization issue so this flush can be eliminated.
+        imageBuffer()->flushGpu(FlushReasonDrawImageOfWebGL);
+    }
+
+    if (originClean() && wouldTaintOrigin(imageSource))
+        setOriginTainted();
+}
+
+void BaseRenderingContext2D::clearCanvas()
+{
+    FloatRect canvasRect(0, 0, width(), height());
+    checkOverdraw(canvasRect, 0, CanvasRenderingContext2DState::NoImage, ClipFill);
+    SkCanvas* c = drawingCanvas();
+    if (c)
+        c->clear(hasAlpha() ? SK_ColorTRANSPARENT : SK_ColorBLACK);
+}
+
+bool BaseRenderingContext2D::rectContainsTransformedRect(const FloatRect& rect, const SkIRect& transformedRect) const
+{
+    FloatQuad quad(rect);
+    FloatQuad transformedQuad(FloatRect(transformedRect.x(), transformedRect.y(), transformedRect.width(), transformedRect.height()));
+    return state().transform().mapQuad(quad).containsQuad(transformedQuad);
+}
+
+CanvasGradient* BaseRenderingContext2D::createLinearGradient(double x0, double y0, double x1, double y1)
+{
+    CanvasGradient* gradient = CanvasGradient::create(FloatPoint(x0, y0), FloatPoint(x1, y1));
+    return gradient;
+}
+
+CanvasGradient* BaseRenderingContext2D::createRadialGradient(double x0, double y0, double r0, double x1, double y1, double r1, ExceptionState& exceptionState)
+{
+    if (r0 < 0 || r1 < 0) {
+        exceptionState.throwDOMException(IndexSizeError, String::format("The %s provided is less than 0.", r0 < 0 ? "r0" : "r1"));
+        return nullptr;
+    }
+
+    CanvasGradient* gradient = CanvasGradient::create(FloatPoint(x0, y0), r0, FloatPoint(x1, y1), r1);
+    return gradient;
+}
+
+CanvasPattern* BaseRenderingContext2D::createPattern(const CanvasImageSourceUnion& imageSource, const String& repetitionType, ExceptionState& exceptionState)
+{
+    Pattern::RepeatMode repeatMode = CanvasPattern::parseRepetitionType(repetitionType, exceptionState);
+    if (exceptionState.hadException())
+        return nullptr;
+
+    SourceImageStatus status;
+    CanvasImageSource* imageSourceInternal = toImageSourceInternal(imageSource);
+    RefPtr<Image> imageForRendering = imageSourceInternal->getSourceImageForCanvas(&status, PreferNoAcceleration, SnapshotReasonCreatePattern);
+
+    switch (status) {
+    case NormalSourceImageStatus:
+        break;
+    case ZeroSizeCanvasSourceImageStatus:
+        exceptionState.throwDOMException(InvalidStateError, String::format("The canvas %s is 0.", imageSourceInternal->elementSize().width() ? "height" : "width"));
+        return nullptr;
+    case UndecodableSourceImageStatus:
+        exceptionState.throwDOMException(InvalidStateError, "Source image is in the 'broken' state.");
+        return nullptr;
+    case InvalidSourceImageStatus:
+        imageForRendering = Image::nullImage();
+        break;
+    case IncompleteSourceImageStatus:
+        return nullptr;
+    default:
+        ASSERT_NOT_REACHED();
+        return nullptr;
+    }
+    ASSERT(imageForRendering);
+
+    bool originClean = !wouldTaintOrigin(imageSourceInternal);
+
+    return CanvasPattern::create(imageForRendering.release(), repeatMode, originClean);
+}
+
+bool BaseRenderingContext2D::computeDirtyRect(const FloatRect& localRect, SkIRect* dirtyRect)
+{
+    SkIRect clipBounds;
+    if (!drawingCanvas()->getClipDeviceBounds(&clipBounds))
+        return false;
+    return computeDirtyRect(localRect, clipBounds, dirtyRect);
+}
+
+bool BaseRenderingContext2D::computeDirtyRect(const FloatRect& localRect, const SkIRect& transformedClipBounds, SkIRect* dirtyRect)
+{
+    FloatRect canvasRect = state().transform().mapRect(localRect);
+
+    if (alphaChannel(state().shadowColor())) {
+        FloatRect shadowRect(canvasRect);
+        shadowRect.move(state().shadowOffset());
+        shadowRect.inflate(state().shadowBlur());
+        canvasRect.unite(shadowRect);
+    }
+
+    SkIRect canvasIRect;
+    static_cast<SkRect>(canvasRect).roundOut(&canvasIRect);
+    if (!canvasIRect.intersect(transformedClipBounds))
+        return false;
+
+    if (dirtyRect)
+        *dirtyRect = canvasIRect;
+
+    return true;
+}
+
+void BaseRenderingContext2D::inflateStrokeRect(FloatRect& rect) const
+{
+    // Fast approximation of the stroke's bounding rect.
+    // This yields a slightly oversized rect but is very fast
+    // compared to Path::strokeBoundingRect().
+    static const double root2 = sqrtf(2);
+    double delta = state().lineWidth() / 2;
+    if (state().lineJoin() == MiterJoin)
+        delta *= state().miterLimit();
+    else if (state().lineCap() == SquareCap)
+        delta *= root2;
+
+    rect.inflate(delta);
+}
+
+bool BaseRenderingContext2D::imageSmoothingEnabled() const
+{
+    return state().imageSmoothingEnabled();
+}
+
+void BaseRenderingContext2D::setImageSmoothingEnabled(bool enabled)
+{
+    if (enabled == state().imageSmoothingEnabled())
+        return;
+
+    modifiableState().setImageSmoothingEnabled(enabled);
+}
+
+String BaseRenderingContext2D::imageSmoothingQuality() const
+{
+    return state().imageSmoothingQuality();
+}
+
+void BaseRenderingContext2D::setImageSmoothingQuality(const String& quality)
+{
+    if (quality == state().imageSmoothingQuality())
+        return;
+
+    modifiableState().setImageSmoothingQuality(quality);
+}
+
+void BaseRenderingContext2D::checkOverdraw(const SkRect& rect, const SkPaint* paint, CanvasRenderingContext2DState::ImageType imageType, DrawType drawType)
+{
+    SkCanvas* c = drawingCanvas();
+    if (!c || !imageBuffer()->isRecording())
+        return;
+
+    SkRect deviceRect;
+    if (drawType == UntransformedUnclippedFill) {
+        deviceRect = rect;
+    } else {
+        ASSERT(drawType == ClipFill);
+        if (state().hasComplexClip())
+            return;
+
+        SkIRect skIBounds;
+        if (!c->getClipDeviceBounds(&skIBounds))
+            return;
+        deviceRect = SkRect::Make(skIBounds);
+    }
+
+    const SkImageInfo& imageInfo = c->imageInfo();
+    if (!deviceRect.contains(SkRect::MakeWH(imageInfo.width(), imageInfo.height())))
+        return;
+
+    bool isSourceOver = true;
+    unsigned alpha = 0xFF;
+    if (paint) {
+        if (paint->getLooper() || paint->getImageFilter() || paint->getMaskFilter())
+            return;
+
+        SkXfermode* xfermode = paint->getXfermode();
+        if (xfermode) {
+            SkXfermode::Mode mode;
+            if (xfermode->asMode(&mode)) {
+                isSourceOver = mode == SkXfermode::kSrcOver_Mode;
+                if (!isSourceOver && mode != SkXfermode::kSrc_Mode && mode != SkXfermode::kClear_Mode)
+                    return; // The code below only knows how to handle Src, SrcOver, and Clear
+            } else {
+                // unknown xfermode
+                ASSERT_NOT_REACHED();
+                return;
+            }
+        }
+
+        alpha = paint->getAlpha();
+
+        if (isSourceOver && imageType == CanvasRenderingContext2DState::NoImage) {
+            SkShader* shader = paint->getShader();
+            if (shader) {
+                if (shader->isOpaque() && alpha == 0xFF)
+                    imageBuffer()->willOverwriteCanvas();
+                return;
+            }
+        }
+    }
+
+    if (isSourceOver) {
+        // With source over, we need to certify that alpha == 0xFF for all pixels
+        if (imageType == CanvasRenderingContext2DState::NonOpaqueImage)
+            return;
+        if (alpha < 0xFF)
+            return;
+    }
+
+    imageBuffer()->willOverwriteCanvas();
+}
+
+DEFINE_TRACE(BaseRenderingContext2D)
+{
+    visitor->trace(m_stateStack);
+}
+
+} // namespace blink