Revert of 2D canvas: remain in deferred rendering mode with canvas to canvas...

Revert of 2D canvas: remain in deferred rendering mode with canvas to canvas drawImage (patchset #2 id:20001 of https://codereview.chromium.org/1288773005/ )

Reason for revert:
Appears to be triggering MSAN crashes: http://test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=virtual%2Fdisplay_list_2d_canvas%2Ffast%2Fcanvas%2F2d.composite.globalAlpha.fillPath.html&testType=layout-tests

Original issue's description:
> 2D canvas: remain in deferred rendering mode with canvas to canvas drawImage
> 
> If the source canvas is not animated, no need to exit deferred rendering
> because there is no risk of memory bloat due to snapshotting.
> 
> BUG=521001
> TEST=telemetry tough_canvas_cases
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=200654

TBR=senorblanco@chromium.org,junov@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=521001

Review URL: https://codereview.chromium.org/1295673003

git-svn-id: svn://svn.chromium.org/blink/trunk@200660 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp

@@ -434,11 +434,6 @@ bool HTMLCanvasElement::is3D() const
     return m_context && m_context->is3d();
 }
 
-bool HTMLCanvasElement::isAnimated2D() const
-{
-    return m_context && m_context->is2d() && hasImageBuffer() && m_imageBuffer->wasDrawnToAfterSnapshot();
-}
-
 void HTMLCanvasElement::setSurfaceSize(const IntSize& size)
 {
     m_size = size;

third_party/WebKit/Source/core/html/HTMLCanvasElement.h

@@ -138,7 +138,6 @@ public:
     AffineTransform baseTransform() const;
 
     bool is3D() const;
-    bool isAnimated2D() const;
 
     bool hasImageBuffer() const { return m_imageBuffer; }
     void discardImageBuffer();

third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.cpp

@@ -1353,20 +1353,6 @@ void CanvasRenderingContext2D::drawImageInternal(SkCanvas* c, CanvasImageSource*
     c->restoreToCount(initialSaveCount);
 }
 
-bool shouldDisableDeferral(CanvasImageSource* imageSource)
-{
-    if (imageSource->isVideoElement())
-        return true;
-    if (imageSource->isCanvasElement()) {
-        HTMLCanvasElement* canvas = static_cast<HTMLCanvasElement*>(imageSource);
-        if (canvas->is3D())
-            return true;
-        if (canvas->isAnimated2D())
-            return true;
-    }
-    return false;
-}
-
 void CanvasRenderingContext2D::drawImage(CanvasImageSource* imageSource,
     float sx, float sy, float sw, float sh,
     float dx, float dy, float dw, float dh, ExceptionState& exceptionState)
@@ -1402,7 +1388,12 @@ void CanvasRenderingContext2D::drawImage(CanvasImageSource* imageSource,
     if (srcRect.isEmpty())
         return;
 
-    if (shouldDisableDeferral(imageSource))
+    // FIXME: crbug.com/521001
+    // We make the destination canvas fall out of display list mode by forcing
+    // immediate rendering. This is to prevent run-away memory consumption caused by SkSurface
+    // copyOnWrite when the source canvas is animated and consumed at a rate higher than the
+    // presentation frame rate of the destination canvas.
+    if (imageSource->isVideoElement() || imageSource->isCanvasElement())
         canvas()->disableDeferral();
 
     validateStateStack();

third_party/WebKit/Source/platform/graphics/ImageBuffer.cpp

@@ -149,9 +149,6 @@ void ImageBuffer::resetCanvas(SkCanvas* canvas) const
 
 PassRefPtr<SkImage> ImageBuffer::newSkImageSnapshot() const
 {
-    if (m_snapshotState == InitialSnapshotState)
-        m_snapshotState = DidAcquireSnapshot;
-
     if (!isSurfaceValid())
         return nullptr;
     return m_surface->newImageSnapshot();
@@ -159,19 +156,14 @@ PassRefPtr<SkImage> ImageBuffer::newSkImageSnapshot() const
 
 PassRefPtr<Image> ImageBuffer::newImageSnapshot() const
 {
-    RefPtr<SkImage> snapshot = newSkImageSnapshot();
+    if (!isSurfaceValid())
+        return nullptr;
+    RefPtr<SkImage> snapshot = m_surface->newImageSnapshot();
     if (!snapshot)
         return nullptr;
     return StaticBitmapImage::create(snapshot);
 }
 
-void ImageBuffer::didDraw(const FloatRect& rect) const
-{
-    if (m_snapshotState == DidAcquireSnapshot)
-        m_snapshotState = DrawnToAfterSnapshot;
-    m_surface->didDraw(rect);
-}
-
 WebLayer* ImageBuffer::platformLayer() const
 {
     return m_surface->layer();

third_party/WebKit/Source/platform/graphics/ImageBuffer.h

@@ -82,8 +82,7 @@ public:
     bool isExpensiveToPaint() const { return m_surface->isExpensiveToPaint(); }
     bool isSurfaceValid() const;
     bool restoreSurface() const;
-    void didDraw(const FloatRect&) const;
-    bool wasDrawnToAfterSnapshot() const { return m_snapshotState == DrawnToAfterSnapshot; }
+    void didDraw(const FloatRect& rect) const { m_surface->didDraw(rect); }
 
     void setFilterQuality(SkFilterQuality filterQuality) { m_surface->setFilterQuality(filterQuality); }
     void setIsHidden(bool hidden) { m_surface->setIsHidden(hidden); }
@@ -139,12 +138,6 @@ public:
 private:
     ImageBuffer(PassOwnPtr<ImageBufferSurface>);
 
-    enum SnapshotState {
-        InitialSnapshotState,
-        DidAcquireSnapshot,
-        DrawnToAfterSnapshot,
-    };
-    mutable SnapshotState m_snapshotState;
     OwnPtr<ImageBufferSurface> m_surface;
     ImageBufferClient* m_client;
 };