Make 2D canvas smarter about chosing whether or not to use GPU acceleration

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

Index: third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.cpp
diff --git a/third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.cpp b/third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.cpp
index 87c61553bbf6441278890508e9e323db66d2a90e..3e5a29fa1b95513189c24f569c39a3fc2181d588 100644
--- a/third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.cpp
+++ b/third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.cpp
@@ -1376,7 +1376,8 @@ void CanvasRenderingContext2D::drawImage(CanvasImageSource* imageSource,
     RefPtr<Image> image;
     SourceImageStatus sourceImageStatus = InvalidSourceImageStatus;
     if (!imageSource->isVideoElement()) {
-        image = imageSource->getSourceImageForCanvas(&sourceImageStatus);
+        AccelerationHint hint = canvas()->buffer()->isAccelerated() ? PreferAcceleration : PreferNoAcceleration;
+        image = imageSource->getSourceImageForCanvas(&sourceImageStatus, hint);
         if (sourceImageStatus == UndecodableSourceImageStatus)
             exceptionState.throwDOMException(InvalidStateError, "The HTMLImageElement provided is in the 'broken' state.");
         if (!image || !image->width() || !image->height())
@@ -1484,7 +1485,7 @@ CanvasPattern* CanvasRenderingContext2D::createPattern(const CanvasImageSourceUn
 
     SourceImageStatus status;
     CanvasImageSource* imageSourceInternal = toImageSourceInternal(imageSource);
-    RefPtr<Image> imageForRendering = imageSourceInternal->getSourceImageForCanvas(&status);
+    RefPtr<Image> imageForRendering = imageSourceInternal->getSourceImageForCanvas(&status, PreferNoAcceleration);
 
     switch (status) {
     case NormalSourceImageStatus:
@@ -1774,6 +1775,10 @@ void CanvasRenderingContext2D::schedulePruneLocalFontCacheIfNeeded()
 
 void CanvasRenderingContext2D::didProcessTask()
 {
+    // The rendering surface needs to be prepared now because it will be too late
+    // to create a layer once we are in the paint invalidation phase.
+    canvas()->prepareSurfaceForPaintingIfNeeded();
+
     pruneLocalFontCache(canvas()->document().canvasFontCache()->maxFonts());
     m_pruneLocalFontCacheScheduled = false;
     Platform::current()->currentThread()->removeTaskObserver(this);