Use SkImage snapshots for ImageBufferSurface texture access

Source/platform/graphics/Canvas2DLayerBridge.cpp

Index: Source/platform/graphics/Canvas2DLayerBridge.cpp
diff --git a/Source/platform/graphics/Canvas2DLayerBridge.cpp b/Source/platform/graphics/Canvas2DLayerBridge.cpp
index a44254c41b5313410576d54207fc2ae432a9f873..1b2abc1ea9a423408b573c85161671c7816b1119 100644
--- a/Source/platform/graphics/Canvas2DLayerBridge.cpp
+++ b/Source/platform/graphics/Canvas2DLayerBridge.cpp
@@ -513,18 +513,14 @@ void Canvas2DLayerBridge::finalizeFrame(const FloatRect &dirtyRect)
     m_didRecordDrawCommand = true;
 }
 
-Platform3DObject Canvas2DLayerBridge::getBackingTexture()
+PassRefPtr<SkImage> Canvas2DLayerBridge::getBackingTextureImage()
 {
-    ASSERT(!m_destructionInProgress);
     if (!checkSurfaceValid())

[f(malita), 2015/06/18 16:33:00]

This is the only place where getBackingTextureImage and newImageSnapshot (below)
diverge - all other implementations are identical.

It would be nice to unify them, but I'm not familiar with this code so not sure
what the implications of adding the check & flush to newImageSnapshot() are.

[Justin Novosad, 2015/06/22 18:22:03]

The check is necessary here, and does not make sense elsewhere. It is so 2D
canvas can handle GPU context losses

-        return 0;
-    m_canvas->flush();
+        return nullptr;
+
     context()->flush();
-    GrRenderTarget* renderTarget = m_canvas->getDevice()->accessRenderTarget();
-    if (renderTarget) {
-        return renderTarget->asTexture()->getTextureHandle();
-    }
-    return 0;
+
+    return adoptRef(m_canvas->newImageSnapshot());
 }
 
 PassRefPtr<SkImage> Canvas2DLayerBridge::newImageSnapshot()