Removing the dependency on GraphicsContext for drawing images in 2D canvas

Source/core/html/HTMLCanvasElement.cpp

Index: Source/core/html/HTMLCanvasElement.cpp
diff --git a/Source/core/html/HTMLCanvasElement.cpp b/Source/core/html/HTMLCanvasElement.cpp
index 49710329fd8e816f698731528da41ff417d1bbb4..d67af461e22994a49f86f5843adbd24a91a55f29 100644
--- a/Source/core/html/HTMLCanvasElement.cpp
+++ b/Source/core/html/HTMLCanvasElement.cpp
@@ -127,7 +127,6 @@ HTMLCanvasElement::~HTMLCanvasElement()
     for (CanvasObserver* canvasObserver : m_observers)
         canvasObserver->canvasDestroyed(this);
     // Ensure these go away before the ImageBuffer.
-    m_contextStateSaver.clear();
     m_context.clear();
 #endif
 }
@@ -289,7 +288,7 @@ void HTMLCanvasElement::didDraw(const FloatRect& rect)
     m_dirtyRect.unite(rect);
     if (m_context && m_context->is2d() && hasImageBuffer())
         buffer()->didDraw(rect);
-    notifyObserversCanvasChanged(m_dirtyRect);
+    notifyObserversCanvasChanged(rect);
 }
 
 void HTMLCanvasElement::didFinalizeFrame()
@@ -370,12 +369,6 @@ void HTMLCanvasElement::reset()
     if (!ok || h < 0)
         h = DefaultHeight;
 
-    if (m_contextStateSaver) {
-        // Reset to the initial graphics context state.
-        m_contextStateSaver->restore();
-        m_contextStateSaver->save();
-    }
-
     if (m_context && m_context->is2d())
         toCanvasRenderingContext2D(m_context.get())->reset();
 
@@ -648,7 +641,6 @@ void HTMLCanvasElement::createImageBuffer()
 void HTMLCanvasElement::createImageBufferInternal(PassOwnPtr<ImageBufferSurface> externalSurface)
 {
     ASSERT(!m_imageBuffer);
-    ASSERT(!m_contextStateSaver);
 
     m_didFailToCreateImageBuffer = true;
     m_imageBufferIsClear = true;
@@ -682,18 +674,11 @@ void HTMLCanvasElement::createImageBufferInternal(PassOwnPtr<ImageBufferSurface>
     }
 
     m_imageBuffer->setClient(this);
-    m_imageBuffer->context()->setShouldClampToSourceRect(false);
-    m_imageBuffer->context()->disableAntialiasingOptimizationForHairlineImages();
-    m_imageBuffer->context()->setImageInterpolationQuality(CanvasDefaultInterpolationQuality);
     // Enabling MSAA overrides a request to disable antialiasing. This is true regardless of whether the
     // rendering mode is accelerated or not. For consistency, we don't want to apply AA in accelerated
     // canvases but not in unaccelerated canvases.
-    if (!msaaSampleCount && document().settings() && !document().settings()->antialiased2dCanvasEnabled())
-        m_imageBuffer->context()->setShouldAntialias(false);
-#if ENABLE(ASSERT)
-    m_imageBuffer->context()->disableDestructionChecks(); // 2D canvas is allowed to leave context in an unfinalized state.
-#endif
-    m_contextStateSaver = adoptPtr(new GraphicsContextStateSaver(*m_imageBuffer->context()));
+    bool disableAntiAliasing = !msaaSampleCount && document().settings() && !document().settings()->antialiased2dCanvasEnabled();
+    toCanvasRenderingContext2D(m_context.get())->setShouldAntialias(!disableAntiAliasing);

[Stephen White, 2015/05/29 17:26:37]

Perhaps we should make the default for CRC2D "should antialias" to be true. Then
we can just disable it here if the flags request it, as before.

 
     if (m_context)
         setNeedsCompositingUpdate();
@@ -749,11 +734,6 @@ void HTMLCanvasElement::updateExternallyAllocatedMemory() const
     m_externallyAllocatedMemory = externallyAllocatedMemory;
 }
 
-GraphicsContext* HTMLCanvasElement::drawingContext() const
-{
-    return buffer() ? m_imageBuffer->context() : nullptr;
-}
-
 SkCanvas* HTMLCanvasElement::drawingCanvas() const
 {
     return buffer() ? m_imageBuffer->canvas() : nullptr;
@@ -814,7 +794,6 @@ PassRefPtr<Image> HTMLCanvasElement::copiedImage(SourceDrawingBuffer sourceBuffe
 
 void HTMLCanvasElement::discardImageBuffer()
 {
-    m_contextStateSaver.clear(); // uses context owned by m_imageBuffer
     m_imageBuffer.clear();
     m_dirtyRect = FloatRect();
     updateExternallyAllocatedMemory();