Enable GPU acceleration in 2D OffscreenCanvases on main thread

third_party/WebKit/Source/modules/offscreencanvas2d/OffscreenCanvasRenderingContext2D.cpp

Index: third_party/WebKit/Source/modules/offscreencanvas2d/OffscreenCanvasRenderingContext2D.cpp
diff --git a/third_party/WebKit/Source/modules/offscreencanvas2d/OffscreenCanvasRenderingContext2D.cpp b/third_party/WebKit/Source/modules/offscreencanvas2d/OffscreenCanvasRenderingContext2D.cpp
index fe38ed1904863ae96ab6bf8be0b35c5ec1d39e52..0d901e4241ba66a9bb46d2e3f47a6ab9b05fa2ca 100644
--- a/third_party/WebKit/Source/modules/offscreencanvas2d/OffscreenCanvasRenderingContext2D.cpp
+++ b/third_party/WebKit/Source/modules/offscreencanvas2d/OffscreenCanvasRenderingContext2D.cpp
@@ -11,6 +11,8 @@
 #include "core/workers/WorkerSettings.h"
 #include "platform/graphics/ImageBuffer.h"
 #include "platform/graphics/StaticBitmapImage.h"
+#include "platform/graphics/UnacceleratedImageBufferSurface.h"
+#include "platform/graphics/gpu/AcceleratedImageBufferSurface.h"
 #include "wtf/Assertions.h"
 
 #define UNIMPLEMENTED ASSERT_NOT_REACHED
@@ -80,12 +82,29 @@ bool OffscreenCanvasRenderingContext2D::hasImageBuffer() const
     return !!m_imageBuffer;
 }
 
+static bool shouldAccelerate(IntSize surfaceSize)
+{
+    if (!isMainThread())
+        return false; // Add support on Workers crbug.com/
+    return RuntimeEnabledFeatures::accelerated2dCanvasEnabled();
+}
+
 ImageBuffer* OffscreenCanvasRenderingContext2D::imageBuffer() const
 {
     if (!m_imageBuffer) {
-        // TODO: crbug.com/593514 Add support for GPU rendering
+        IntSize surfaceSize(width(), height());
+        OpacityMode opacityMode = m_hasAlpha ? NonOpaque : Opaque;
+        std::unique_ptr<ImageBufferSurface> surface;
+        if (shouldAccelerate(surfaceSize)) {
+            surface.reset(new AcceleratedImageBufferSurface(surfaceSize, opacityMode));
+        }
+
+        if (!surface || !surface->isValid()) {
+            surface.reset(new UnacceleratedImageBufferSurface(surfaceSize, opacityMode, InitializeImagePixels));
+        }
+
         OffscreenCanvasRenderingContext2D* nonConstThis = const_cast<OffscreenCanvasRenderingContext2D*>(this);
-        nonConstThis->m_imageBuffer = ImageBuffer::create(IntSize(width(), height()), m_hasAlpha ? NonOpaque : Opaque, InitializeImagePixels);
+        nonConstThis->m_imageBuffer = ImageBuffer::create(std::move(surface));
 
         if (m_needsMatrixClipRestore) {
             restoreMatrixClipStack(m_imageBuffer->canvas());
@@ -100,8 +119,8 @@ ImageBitmap* OffscreenCanvasRenderingContext2D::transferToImageBitmap(ExceptionS
 {
     if (!imageBuffer())
         return nullptr;
-    // TODO: crbug.com/593514 Add support for GPU rendering
-    RefPtr<SkImage> skImage = m_imageBuffer->newSkImageSnapshot(PreferNoAcceleration, SnapshotReasonTransferToImageBitmap);
+    RefPtr<SkImage> skImage = m_imageBuffer->newSkImageSnapshot(PreferAcceleration, SnapshotReasonTransferToImageBitmap);
+    DCHECK(isMainThread() || !skImage->isTextureBacked()); // Acceleration not yet supported in Workers
     RefPtr<StaticBitmapImage> image = StaticBitmapImage::create(skImage.release());
     image->setOriginClean(this->originClean());
     m_imageBuffer.reset(); // "Transfer" means no retained buffer