Use SkImage as a backing store for copying 2d Contexts to ImageBitmaps.

Source/core/page/ImageBitmap.cpp

Index: Source/core/page/ImageBitmap.cpp
diff --git a/Source/core/page/ImageBitmap.cpp b/Source/core/page/ImageBitmap.cpp
index ffe3af0dfa65d59ae71c04122efe6fad942d5949..e4a738814bc82312b1d75f7dc4402634b497ba52 100644
--- a/Source/core/page/ImageBitmap.cpp
+++ b/Source/core/page/ImageBitmap.cpp
@@ -35,6 +35,8 @@ static inline PassRefPtr<Image> cropImage(Image* image, const IntRect& cropRect)
 ImageBitmap::ImageBitmap(HTMLImageElement* image, const IntRect& cropRect)
     : m_cropRect(cropRect)
     , m_imageElement(image)
+    , m_bitmap(0)
+    , m_derivedFromCanvas(false)
 {
     m_imageElement->addClient(this);
 
@@ -49,6 +51,7 @@ ImageBitmap::ImageBitmap(HTMLVideoElement* video, const IntRect& cropRect)
     : m_cropRect(cropRect)
     , m_imageElement(0)
     , m_bitmapOffset(IntPoint())
+    , m_derivedFromCanvas(false)
 {
     IntRect videoRect = IntRect(IntPoint(), video->player()->naturalSize());
     IntRect srcRect = intersection(cropRect, videoRect);
@@ -68,16 +71,13 @@ ImageBitmap::ImageBitmap(HTMLVideoElement* video, const IntRect& cropRect)
 ImageBitmap::ImageBitmap(HTMLCanvasElement* canvas, const IntRect& cropRect)
     : m_cropRect(cropRect)
     , m_imageElement(0)
+    , m_bitmap(canvas->buffer()->imageSnapshot())
     , m_bitmapOffset(IntPoint())
+    , m_derivedFromCanvas(true)
 {
-    IntSize canvasSize = canvas->size();
-    IntRect srcRect = intersection(cropRect, IntRect(IntPoint(), canvasSize));
-    IntRect dstRect(IntPoint(), srcRect.size());
-
-    m_buffer = ImageBuffer::create(canvasSize);
-    m_buffer->context()->drawImageBuffer(canvas->buffer(), dstRect, srcRect);
-    m_bitmap = m_buffer->copyImage(DontCopyBackingStore);
+    IntRect srcRect = intersection(cropRect, IntRect(IntPoint(), canvas->size()));
     m_bitmapRect = IntRect(IntPoint(max(0, -cropRect.x()), max(0, -cropRect.y())), srcRect.size());
+    m_bitmapOffset = srcRect.location();
 
     ScriptWrappable::init(this);
 }
@@ -86,6 +86,7 @@ ImageBitmap::ImageBitmap(ImageData* data, const IntRect& cropRect)
     : m_cropRect(cropRect)
     , m_imageElement(0)
     , m_bitmapOffset(IntPoint())
+    , m_derivedFromCanvas(false)
 {
     IntRect srcRect = intersection(cropRect, IntRect(IntPoint(), data->size()));
 
@@ -103,19 +104,24 @@ ImageBitmap::ImageBitmap(ImageBitmap* bitmap, const IntRect& cropRect)
     : m_cropRect(cropRect)
     , m_imageElement(bitmap->imageElement())
     , m_bitmapOffset(IntPoint())
+    , m_derivedFromCanvas(bitmap->derivedFromCanvas())
 {
     IntRect oldBitmapRect = bitmap->bitmapRect();
     IntRect srcRect = intersection(cropRect, oldBitmapRect);
     m_bitmapRect = IntRect(IntPoint(max(0, oldBitmapRect.x() - cropRect.x()), max(0, oldBitmapRect.y() - cropRect.y())), srcRect.size());
 
     if (m_imageElement) {
-        m_imageElement->addClient(this);
         m_bitmap = 0;
+        m_imageElement->addClient(this);
+        m_bitmapOffset = srcRect.location();
+    } else if (m_derivedFromCanvas) {
+        m_bitmap = bitmap->bitmapImage();
         m_bitmapOffset = srcRect.location();
     } else {
-        IntRect adjustedCropRect(IntPoint(cropRect.x() -oldBitmapRect.x(), cropRect.y() - oldBitmapRect.y()), cropRect.size());
+        IntRect adjustedCropRect(IntPoint(cropRect.x() - oldBitmapRect.x(), cropRect.y() - oldBitmapRect.y()), cropRect.size());
         m_bitmap = cropImage(bitmap->bitmapImage().get(), adjustedCropRect);
     }
+
     ScriptWrappable::init(this);
 }
 
@@ -170,6 +176,8 @@ void ImageBitmap::notifyImageSourceChanged()
 PassRefPtr<Image> ImageBitmap::bitmapImage() const
 {
     ASSERT((m_imageElement || m_bitmap) && (!m_imageElement || !m_bitmap));
+    ASSERT((m_imageElement || m_derivedFromCanvas) && (!m_imageElement || !m_derivedFromCanvas));
+
     if (m_imageElement)
         return m_imageElement->cachedImage()->image();
     return m_bitmap;