2D canvas: remain in deferred rendering mode with canvas to canvas drawImage

Source/platform/graphics/ImageBuffer.cpp

Index: Source/platform/graphics/ImageBuffer.cpp
diff --git a/Source/platform/graphics/ImageBuffer.cpp b/Source/platform/graphics/ImageBuffer.cpp
index 12a631e173a4618d5632b44681869de5f3be4717..e69d87a7a380dab35bb8c7a9d3c98f886d313a58 100644
--- a/Source/platform/graphics/ImageBuffer.cpp
+++ b/Source/platform/graphics/ImageBuffer.cpp
@@ -78,6 +78,7 @@ PassOwnPtr<ImageBuffer> ImageBuffer::create(const IntSize& size, OpacityMode opa
 ImageBuffer::ImageBuffer(PassOwnPtr<ImageBufferSurface> surface)
     : m_surface(surface)
     , m_client(0)
+    , m_snapshotState(InitialSnapshotState)
 {
     m_surface->setImageBuffer(this);
 }
@@ -149,6 +150,9 @@ 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();
@@ -156,14 +160,19 @@ PassRefPtr<SkImage> ImageBuffer::newSkImageSnapshot() const
 
 PassRefPtr<Image> ImageBuffer::newImageSnapshot() const
 {
-    if (!isSurfaceValid())
-        return nullptr;
-    RefPtr<SkImage> snapshot = m_surface->newImageSnapshot();
+    RefPtr<SkImage> snapshot = newSkImageSnapshot();
     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();