Expose if we are using swiftshader via WebGraphicsContext3DProvider.

third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp

 /*
  * Copyright (C) 2004, 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 742 matching lines @@
     return document().getSecurityOrigin();
 }
 
 bool HTMLCanvasElement::originClean() const
 {
     if (document().settings() && document().settings()->disableReadingFromCanvas())
         return false;
     return m_originClean;
 }
 
-bool HTMLCanvasElement::shouldAccelerate(const IntSize& size) const
+bool HTMLCanvasElement::shouldAccelerate(const IntSize& size, const WebGraphicsContext3DProvider* sharedMainThreadContextProvider) const
 {
     if (m_context && !m_context->is2d())
         return false;
 
     if (RuntimeEnabledFeatures::forceDisplayList2dCanvasEnabled())
         return false;
 
     if (!RuntimeEnabledFeatures::accelerated2dCanvasEnabled())
         return false;
 
     // The following is necessary for handling the special case of canvases in the
     // dev tools overlay, which run in a process that supports accelerated 2d canvas
     // but in a special compositing context that does not.
     if (layoutBox() && !layoutBox()->hasAcceleratedCompositing())
         return false;
 
-    int canvasPixelCount = size.width() * size.height();
+    CheckedNumeric<int> checkedCanvasPixelCount = size.width();
+    checkedCanvasPixelCount *= size.height();
+    if (!checkedCanvasPixelCount.IsValid())
+        return false;
+    int canvasPixelCount = checkedCanvasPixelCount.ValueOrDie();
 
     if (RuntimeEnabledFeatures::displayList2dCanvasEnabled()) {
 #if 0
         // TODO(junov): re-enable this code once we solve the problem of recording
         // GPU-backed images to an SkPicture for cross-context rendering crbug.com/490328
 
         // If the compositor provides GPU acceleration to display list canvases, we
         // prefer that over direct acceleration.
         if (document().viewportDescription().matchesHeuristicsForGpuRasterization())
             return false;
 #endif
         // If the GPU resources would be very expensive, prefer a display list.
         if (canvasPixelCount > ExpensiveCanvasHeuristicParameters::PreferDisplayListOverGpuSizeThreshold)
             return false;
     }
 
     // Do not use acceleration for small canvas.
     Settings* settings = document().settings();
     if (!settings || canvasPixelCount < settings->minimumAccelerated2dCanvasSize())
         return false;
 
-    if (!Platform::current()->canAccelerate2dCanvas())
+    if (sharedMainThreadContextProvider->isSoftwareRendering())
         return false;
 
     // When GPU allocated memory runs low (due to having created too many
     // accelerated canvases), the compositor starves and browser becomes laggy.
     // Thus, we should stop allocating more GPU memory to new canvases created
     // when the current memory usage exceeds the threshold.
     if (ImageBuffer::getGlobalGPUMemoryUsage() >= MaxGlobalGPUMemoryUsage)
         return false;
 
     // Allocating too many GPU resources can makes us run into the driver's
@@ skipping 31 matching lines @@
     OpacityMode opacityMode = !m_context || m_context->hasAlpha() ? NonOpaque : Opaque;
 
     *msaaSampleCount = 0;
     if (is3D()) {
         // If 3d, but the use of the canvas will be for non-accelerated content
         // then make a non-accelerated ImageBuffer. This means copying the internal
         // Image will require a pixel readback, but that is unavoidable in this case.
         return wrapUnique(new AcceleratedImageBufferSurface(deviceSize, opacityMode));
     }
 
-    if (shouldAccelerate(deviceSize)) {
+    std::unique_ptr<WebGraphicsContext3DProvider> contextProvider = wrapUnique(Platform::current()->createSharedOffscreenGraphicsContext3DProvider());
+    if (!contextProvider) {
+        CanvasMetrics::countCanvasContextUsage(CanvasMetrics::Accelerated2DCanvasGPUContextLost);
+    } else if (shouldAccelerate(deviceSize, contextProvider.get())) {
         if (document().settings())
             *msaaSampleCount = document().settings()->accelerated2dCanvasMSAASampleCount();
-        std::unique_ptr<ImageBufferSurface> surface = wrapUnique(new Canvas2DImageBufferSurface(deviceSize, *msaaSampleCount, opacityMode, Canvas2DLayerBridge::EnableAcceleration));
+        std::unique_ptr<ImageBufferSurface> surface = wrapUnique(new Canvas2DImageBufferSurface(std::move(contextProvider), deviceSize, *msaaSampleCount, opacityMode, Canvas2DLayerBridge::EnableAcceleration));
         if (surface->isValid()) {
             CanvasMetrics::countCanvasContextUsage(CanvasMetrics::GPUAccelerated2DCanvasImageBufferCreated);
             return surface;
         }
         CanvasMetrics::countCanvasContextUsage(CanvasMetrics::GPUAccelerated2DCanvasImageBufferCreationFailed);
     }
 
     std::unique_ptr<RecordingImageBufferFallbackSurfaceFactory> surfaceFactory = wrapUnique(new UnacceleratedSurfaceFactory());
 
     if (shouldUseDisplayList(deviceSize)) {
@@ skipping 368 matching lines @@
 
 bool HTMLCanvasElement::createSurfaceLayer()
 {
     DCHECK(!m_surfaceLayerBridge);
     std::unique_ptr<CanvasSurfaceLayerBridgeClient> bridgeClient = wrapUnique(new CanvasSurfaceLayerBridgeClientImpl());
     m_surfaceLayerBridge = wrapUnique(new CanvasSurfaceLayerBridge(std::move(bridgeClient)));
     return m_surfaceLayerBridge->createSurfaceLayer(this->width(), this->height());
 }
 
 } // namespace blink