Fixing 2D canvas invalidation region tracking.

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 f5eb85e735415ef9707a1b6dc70e5144a855bb3e..e8ee49e8031ee9b1cc80e4fc4abc0357f639bd5b 100644
--- a/Source/platform/graphics/ImageBuffer.cpp
+++ b/Source/platform/graphics/ImageBuffer.cpp
@@ -123,6 +123,12 @@ void ImageBuffer::notifySurfaceInvalid()
         m_client->notifySurfaceInvalid();
 }
 
+void ImageBuffer::didPresent()

[Stephen White, 2014/07/17 15:28:19]

It seems unfortunate that ImageBuffer has all this functionality that's not
really related to being a leaf class bag o' pixels. But I guess that ship has
sailed.

+{
+    if (m_client)
+        m_client->didPresent();
+}
+
 static SkBitmap deepSkBitmapCopy(const SkBitmap& bitmap)
 {
     SkBitmap tmp;