Allow eviction of ImageBitmaps that are created from ImageElements.

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 fabe6847b5aabfeb1a3482cb5754b9cbb20caddd..9a0df9795314984a9c1fc09c0470eff97e7b1060 100644
--- a/Source/core/page/ImageBitmap.cpp
+++ b/Source/core/page/ImageBitmap.cpp
@@ -9,7 +9,7 @@
 #include "core/html/HTMLImageElement.h"
 #include "core/html/HTMLVideoElement.h"
 #include "core/html/ImageData.h"
-#include "core/page/ImageBitmapCallback.h"
+#include "core/platform/graphics/BitmapImage.h"
 #include "core/platform/graphics/GraphicsContext.h"
 #include "wtf/RefPtr.h"
 
@@ -17,7 +17,7 @@ using namespace std;
 
 namespace WebCore {
 
-static inline IntRect normalizeRect(const IntRect rect)
+static inline IntRect normalizeRect(const IntRect& rect)
 {
     return IntRect(min(rect.x(), rect.maxX()),
         min(rect.y(), rect.maxY()),
@@ -25,26 +25,26 @@ static inline IntRect normalizeRect(const IntRect rect)
         max(rect.height(), -rect.height()));
 }
 
-static inline PassRefPtr<BitmapImage> cropImage(Image* image, IntRect cropRect)
+static inline PassRefPtr<Image> cropImage(Image* image, const IntRect& cropRect)
 {
     SkBitmap cropped;
     image->nativeImageForCurrentFrame()->bitmap().extractSubset(&cropped, cropRect);
     return BitmapImage::create(NativeImageSkia::create(cropped));
 }
 
-ImageBitmap::ImageBitmap(HTMLImageElement* image, IntRect cropRect)
+ImageBitmap::ImageBitmap(HTMLImageElement* image, const IntRect& cropRect)
     : m_bitmapOffset(max(0, -cropRect.x()), max(0, -cropRect.y()))
-    , m_size(cropRect.size())
+    , m_cropRect(cropRect)
 {
-    Image* bitmapImage = image->cachedImage()->image();
-    m_bitmap = cropImage(bitmapImage, cropRect).get();
+    m_bitmap = new CachedImage(cropImage(image->cachedImage()->image(), cropRect).get());

[Justin Novosad, 2013/07/23 16:55:12]

Why a new cached image? can we not take a ref on the original cached image. 
What happens if we try to use the ImageBitmap after its cached image is dropped
from the decode cache?  Expected behavior is for the image to be re-decoded in
that case. I don't see how that can happen with this code since we are losing
track of the source resource.

+    m_bitmap->setDecodePriority(CachedResource::DecodePriorityHigh);
 
     ScriptWrappable::init(this);
 }
 
-ImageBitmap::ImageBitmap(HTMLVideoElement* video, IntRect cropRect)
+ImageBitmap::ImageBitmap(HTMLVideoElement* video, const IntRect& cropRect)
     : m_bitmapOffset(max(0, -cropRect.x()), max(0, -cropRect.y()))
-    , m_size(cropRect.size())
+    , m_cropRect(cropRect)
 {
     IntRect videoRect = IntRect(IntPoint(), video->player()->naturalSize());
     IntRect srcRect = intersection(cropRect, videoRect);
@@ -55,14 +55,15 @@ ImageBitmap::ImageBitmap(HTMLVideoElement* video, IntRect cropRect)
     c->clip(dstRect);
     c->translate(-srcRect.x(), -srcRect.y());
     video->paintCurrentFrameInContext(c, videoRect);
-    m_bitmap = static_cast<BitmapImage*>(m_buffer->copyImage(DontCopyBackingStore).get());
+    m_bitmap = new CachedImage(m_buffer->copyImage(DontCopyBackingStore).get());

[Justin Novosad, 2013/07/23 16:55:12]

When creating from a video, we have no way to regenerate the image if it is ever
discarded from cache, so this should not be a cached image. It should continue
to be a copy store in a BitmapImage.

+    m_bitmap->setDecodePriority(CachedResource::DecodePriorityHigh);
 
     ScriptWrappable::init(this);
 }
 
-ImageBitmap::ImageBitmap(HTMLCanvasElement* canvas, IntRect cropRect)
+ImageBitmap::ImageBitmap(HTMLCanvasElement* canvas, const IntRect& cropRect)
     : m_bitmapOffset(max(0, -cropRect.x()), max(0, -cropRect.y()))
-    , m_size(cropRect.size())
+    , m_cropRect(cropRect)
 {
     IntSize canvasSize = canvas->size();
     IntRect srcRect = intersection(cropRect, IntRect(IntPoint(), canvasSize));
@@ -70,14 +71,15 @@ ImageBitmap::ImageBitmap(HTMLCanvasElement* canvas, IntRect cropRect)
 
     m_buffer = ImageBuffer::create(canvasSize);
     m_buffer->context()->drawImageBuffer(canvas->buffer(), dstRect, srcRect);
-    m_bitmap = static_cast<BitmapImage*>(m_buffer->copyImage(DontCopyBackingStore).get());
+    m_bitmap = new CachedImage(m_buffer->copyImage(DontCopyBackingStore).get());

[Justin Novosad, 2013/07/23 16:55:12]

Same here.  This should not ba a cached image.

+    m_bitmap->setDecodePriority(CachedResource::DecodePriorityHigh);
 
     ScriptWrappable::init(this);
 }
 
-ImageBitmap::ImageBitmap(ImageData* data, IntRect cropRect)
+ImageBitmap::ImageBitmap(ImageData* data, const IntRect& cropRect)
     : m_bitmapOffset(max(0, -cropRect.x()), max(0, -cropRect.y()))
-    , m_size(cropRect.size())
+    , m_cropRect(cropRect)
 {
     IntRect srcRect = intersection(cropRect, IntRect(IntPoint(), data->size()));
 
@@ -85,51 +87,53 @@ ImageBitmap::ImageBitmap(ImageData* data, IntRect cropRect)
     if (srcRect.width() > 0 && srcRect.height() > 0)
         m_buffer->putByteArray(Unmultiplied, data->data(), data->size(), srcRect, IntPoint(min(0, -cropRect.x()), min(0, -cropRect.y())));
 
-    m_bitmap = static_cast<BitmapImage*>(m_buffer->copyImage(DontCopyBackingStore).get());
+    m_bitmap = new CachedImage(m_buffer->copyImage(DontCopyBackingStore).get());

[Justin Novosad, 2013/07/23 16:55:12]

Should not be a cached image

+    m_bitmap->setDecodePriority(CachedResource::DecodePriorityHigh);
 
     ScriptWrappable::init(this);
 }
 
-ImageBitmap::ImageBitmap(ImageBitmap* bitmap, IntRect cropRect)
+ImageBitmap::ImageBitmap(ImageBitmap* bitmap, const IntRect& cropRect)
     : m_bitmapOffset(max(0, bitmap->bitmapOffset().x() - cropRect.x()), max(0, bitmap->bitmapOffset().y() - cropRect.y()))
-    , m_size(cropRect.size())
+    , m_cropRect(cropRect)
 {
-    Image* bitmapImage = bitmap->bitmapImage();
-    cropRect.moveBy(IntPoint(-bitmap->bitmapOffset().x(), -bitmap->bitmapOffset().y()));
-    m_bitmap = cropImage(bitmapImage, cropRect).get();
+    IntRect adjustedCropRect(IntPoint(cropRect.x() - bitmap->bitmapOffset().x(), cropRect.y() - bitmap->bitmapOffset().y()), cropRect.size());
+
+    m_bitmap = new CachedImage(cropImage(bitmap->bitmapImage(), adjustedCropRect).get());

[Justin Novosad, 2013/07/23 16:55:12]

This function needs to be more complex. It should share resource when possible
and it should only have a CachedImage if the source has a CachedImage.

+    m_bitmap->setDecodePriority(CachedResource::DecodePriorityHigh);
 
     ScriptWrappable::init(this);
 }
 
-PassRefPtr<ImageBitmap> ImageBitmap::create(HTMLImageElement* image, IntRect cropRect)
+PassRefPtr<ImageBitmap> ImageBitmap::create(HTMLImageElement* image, const IntRect& cropRect)
 {
     IntRect normalizedCropRect = normalizeRect(cropRect);
-    RefPtr<ImageBitmap> imageBitmap(adoptRef(new ImageBitmap(image, normalizedCropRect)));
+    RefPtr<ImageBitmap> imageBitmap(adoptRef(new ImageBitmap( image, normalizedCropRect)));
     return imageBitmap.release();
 }
 
-PassRefPtr<ImageBitmap> ImageBitmap::create(HTMLVideoElement* video, IntRect cropRect)
+PassRefPtr<ImageBitmap> ImageBitmap::create(HTMLVideoElement* video, const IntRect& cropRect)
 {
     IntRect normalizedCropRect = normalizeRect(cropRect);
     RefPtr<ImageBitmap> imageBitmap(adoptRef(new ImageBitmap(video, normalizedCropRect)));
     return imageBitmap.release();
 }
 
-PassRefPtr<ImageBitmap> ImageBitmap::create(HTMLCanvasElement* canvas, IntRect cropRect)
+PassRefPtr<ImageBitmap> ImageBitmap::create(HTMLCanvasElement* canvas, const IntRect& cropRect)
 {
     IntRect normalizedCropRect = normalizeRect(cropRect);
     RefPtr<ImageBitmap> imageBitmap(adoptRef(new ImageBitmap(canvas, normalizedCropRect)));
     return imageBitmap.release();
 }
 
-PassRefPtr<ImageBitmap> ImageBitmap::create(ImageData* data, IntRect cropRect)
+PassRefPtr<ImageBitmap> ImageBitmap::create(ImageData* data, const IntRect& cropRect)
 {
     IntRect normalizedCropRect = normalizeRect(cropRect);
     RefPtr<ImageBitmap> imageBitmap(adoptRef(new ImageBitmap(data, normalizedCropRect)));
     return imageBitmap.release();
 }
 
-PassRefPtr<ImageBitmap> ImageBitmap::create(ImageBitmap* bitmap, IntRect cropRect)
+PassRefPtr<ImageBitmap> ImageBitmap::create(ImageBitmap* bitmap, const IntRect& cropRect)
 {
     IntRect normalizedCropRect = normalizeRect(cropRect);
     RefPtr<ImageBitmap> imageBitmap(adoptRef(new ImageBitmap(bitmap, normalizedCropRect)));