Expose if we are using swiftshader via WebGraphicsContext3DProvider.

third_party/WebKit/Source/platform/graphics/Canvas2DLayerBridge.cpp

 /*
  * Copyright (C) 2012 Google Inc. 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.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 72 matching lines @@
     if (surface) {
         if (opacityMode == Opaque) {
             surface->getCanvas()->clear(SK_ColorBLACK);
         } else {
             surface->getCanvas()->clear(SK_ColorTRANSPARENT);
         }
     }
     return fromSkSp(surface);
 }
 
-PassRefPtr<Canvas2DLayerBridge> Canvas2DLayerBridge::create(const IntSize& size, int msaaSampleCount, OpacityMode opacityMode, AccelerationMode accelerationMode)
-{
-    TRACE_EVENT_INSTANT0("test_gpu", "Canvas2DLayerBridgeCreation", TRACE_EVENT_SCOPE_GLOBAL);
-    std::unique_ptr<WebGraphicsContext3DProvider> contextProvider = wrapUnique(Platform::current()->createSharedOffscreenGraphicsContext3DProvider());
-    if (!contextProvider)
-        return nullptr;
-    RefPtr<Canvas2DLayerBridge> layerBridge;
-    layerBridge = adoptRef(new Canvas2DLayerBridge(std::move(contextProvider), size, msaaSampleCount, opacityMode, accelerationMode));
-    return layerBridge.release();
-}
-
 Canvas2DLayerBridge::Canvas2DLayerBridge(std::unique_ptr<WebGraphicsContext3DProvider> contextProvider, const IntSize& size, int msaaSampleCount, OpacityMode opacityMode, AccelerationMode accelerationMode)
     : m_contextProvider(std::move(contextProvider))
     , m_logger(wrapUnique(new Logger))
     , m_weakPtrFactory(this)
     , m_imageBuffer(0)
     , m_msaaSampleCount(msaaSampleCount)
     , m_bytesAllocated(0)
     , m_haveRecordedDrawCommands(false)
     , m_destructionInProgress(false)
     , m_filterQuality(kLow_SkFilterQuality)
@@ skipping 682 matching lines @@
     // context that it can use (each time it tries it loses our context).
     // But checkSurfaceValid() returns true even tho there is a GL error
     // sometimes.. so not sure if just checking for a GL error is right here
     // or what.
     if (useSharedMemory) {
         // Since we're going to software compositing, this class will soon be
         // destroyed for software mode canvas.
         return false;
     }
 
+    // If the context is lost, we don't know if we should be producing GPU or

[danakj, 2016/08/22 22:57:44]

I made Canvas2DLB check for context loss explicitly, and return false in this
case, so it's not going to ever give to cc a GPU frame when cc has already
switched to using software. This matches DrawingBuffer.

+    // software frames, until we get a new context, since the compositor will
+    // be trying to get a new context and may change modes.
+    if (m_contextProvider->contextGL()->GetGraphicsResetStatusKHR() != GL_NO_ERROR)
+        return false;
+
     RefPtr<SkImage> image = newImageSnapshot(PreferAcceleration, SnapshotReasonUnknown);
     if (!image || !image->getTexture())
         return false;
 
     // Early exit if canvas was not drawn to since last prepareMailbox.
     GLenum filter = getGLFilter();
     if (image->uniqueID() == m_lastImageId && filter == m_lastFilter)
         return false;
     m_lastImageId = image->uniqueID();
     m_lastFilter = filter;
@@ skipping 186 matching lines @@
 Canvas2DLayerBridge::MailboxInfo::MailboxInfo() = default;
 Canvas2DLayerBridge::MailboxInfo::MailboxInfo(const MailboxInfo& other) = default;
 
 void Canvas2DLayerBridge::Logger::reportHibernationEvent(HibernationEvent event)
 {
     DEFINE_STATIC_LOCAL(EnumerationHistogram, hibernationHistogram, ("Canvas.HibernationEvents", HibernationEventCount));
     hibernationHistogram.count(event);
 }
 
 } // namespace blink