Move overdraw tracking code from GraphicsContext to CanvasRenderingContext2D

Source/core/html/HTMLCanvasElement.cpp

Index: Source/core/html/HTMLCanvasElement.cpp
diff --git a/Source/core/html/HTMLCanvasElement.cpp b/Source/core/html/HTMLCanvasElement.cpp
index 1c2a8180f7870b72fc0a0db4e3acf48a3e621790..f8db1d2de7de8a593be8143c001474461dc517f7 100644
--- a/Source/core/html/HTMLCanvasElement.cpp
+++ b/Source/core/html/HTMLCanvasElement.cpp
@@ -591,7 +591,7 @@ PassOwnPtr<ImageBufferSurface> HTMLCanvasElement::createImageBufferSurface(const
         OwnPtr<ImageBufferSurface> surface = adoptPtr(new RecordingImageBufferSurface(deviceSize, surfaceFactory.release(), opacityMode));
         if (surface->isValid())
             return surface.release();
-        surfaceFactory = createSurfaceFactory(deviceSize, msaaSampleCount); // recreate because old previous one was released
+        surfaceFactory = createSurfaceFactory(deviceSize, msaaSampleCount); // recreate because previous one was released
     }
 
     return surfaceFactory->createSurface(deviceSize, opacityMode);
@@ -599,12 +599,12 @@ PassOwnPtr<ImageBufferSurface> HTMLCanvasElement::createImageBufferSurface(const
 
 void HTMLCanvasElement::createImageBuffer()
 {
-    createImageBufferInternal();
+    createImageBufferInternal(nullptr);
     if (m_didFailToCreateImageBuffer && m_context->is2d())
         toCanvasRenderingContext2D(m_context.get())->loseContext();
 }
 
-void HTMLCanvasElement::createImageBufferInternal()
+void HTMLCanvasElement::createImageBufferInternal(PassOwnPtr<ImageBufferSurface> externalSurface)
 {
     ASSERT(!m_imageBuffer);
     ASSERT(!m_contextStateSaver);
@@ -615,8 +615,13 @@ void HTMLCanvasElement::createImageBufferInternal()
     if (!canCreateImageBuffer(size()))
         return;
 
-    int msaaSampleCount;
-    OwnPtr<ImageBufferSurface> surface = createImageBufferSurface(size(), &msaaSampleCount);
+    int msaaSampleCount = 0;
+    OwnPtr<ImageBufferSurface> surface;
+    if (externalSurface) {
+        surface = externalSurface;
+    } else {
+        surface = createImageBufferSurface(size(), &msaaSampleCount);
+    }
     m_imageBuffer = ImageBuffer::create(surface.release());
     if (!m_imageBuffer)
         return;
@@ -732,6 +737,12 @@ ImageBuffer* HTMLCanvasElement::buffer() const
     return m_imageBuffer.get();
 }
 
+void HTMLCanvasElement::createImageBufferUsingSurface(PassOwnPtr<ImageBufferSurface> surface)
+{
+    discardImageBuffer();
+    createImageBufferInternal(surface);
+}
+
 void HTMLCanvasElement::ensureUnacceleratedImageBuffer()
 {
     ASSERT(m_context);
@@ -855,4 +866,9 @@ FloatSize HTMLCanvasElement::sourceSize() const
     return FloatSize(width(), height());
 }
 
+bool HTMLCanvasElement::isOpaque() const
+{
+    return m_context && !m_context->hasAlpha();
 }
+
+} // blink