Expose if we are using swiftshader via WebGraphicsContext3DProvider.

content/renderer/renderer_blink_platform_impl.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/renderer/renderer_blink_platform_impl.h"
 
 #include <utility>
 
 #include "base/command_line.h"
 #include "base/files/file_path.h"
@@ skipping 662 matching lines @@
   return DatabaseUtil::DatabaseSetFileSize(
       vfs_file_name, size, sync_message_filter_.get());
 }
 
 WebString RendererBlinkPlatformImpl::databaseCreateOriginIdentifier(
     const blink::WebSecurityOrigin& origin) {
   return WebString::fromUTF8(storage::GetIdentifierFromOrigin(
       WebSecurityOriginToGURL(origin)));
 }
 
-bool RendererBlinkPlatformImpl::canAccelerate2dCanvas() {
-  RenderThreadImpl* thread = RenderThreadImpl::current();
-  scoped_refptr<gpu::GpuChannelHost> host = thread->EstablishGpuChannelSync();
-  if (!host)
-    return false;
-
-  return !host->gpu_info().software_rendering;
-}
-
 bool RendererBlinkPlatformImpl::isThreadedCompositingEnabled() {
   RenderThreadImpl* thread = RenderThreadImpl::current();
   // thread can be NULL in tests.
   return thread && thread->compositor_task_runner().get();
 }
 
 bool RendererBlinkPlatformImpl::isThreadedAnimationEnabled() {
   RenderThreadImpl* thread = RenderThreadImpl::current();
   return thread ? thread->IsThreadedAnimationEnabled() : true;
 }
@@ skipping 376 matching lines @@
     auto* gl = share_provider_impl->contextGL();
     if (gl->GetGraphicsResetStatusKHR() != GL_NO_ERROR) {
       std::string error_message(
           "OffscreenContext Creation failed, Shared context is lost");
       gl_info->errorMessage = WebString::fromUTF8(error_message);
       return nullptr;
     }
     share_context = share_provider_impl->context_provider();
   }
 
+  bool is_software_rendering = gpu_channel_host->gpu_info().software_rendering;
+
   // This is an offscreen context, which doesn't use the default frame buffer,
   // so don't request any alpha, depth, stencil, antialiasing.
   gpu::gles2::ContextCreationAttribHelper attributes;
   attributes.alpha_size = -1;
   attributes.depth_size = 0;
   attributes.stencil_size = 0;
   attributes.samples = 0;
   attributes.sample_buffers = 0;
   attributes.bind_generates_resource = false;
   // Prefer discrete GPU for WebGL.
@@ skipping 11 matching lines @@
   constexpr bool automatic_flushes = true;
   constexpr bool support_locking = false;
 
   scoped_refptr<ContextProviderCommandBuffer> provider(
       new ContextProviderCommandBuffer(
           std::move(gpu_channel_host), gpu::GPU_STREAM_DEFAULT,
           gpu::GpuStreamPriority::NORMAL, gpu::kNullSurfaceHandle,
           GURL(top_document_web_url), automatic_flushes, support_locking,
           gpu::SharedMemoryLimits(), attributes, share_context,
           command_buffer_metrics::OFFSCREEN_CONTEXT_FOR_WEBGL));
-  return new WebGraphicsContext3DProviderImpl(std::move(provider));
+  return new WebGraphicsContext3DProviderImpl(std::move(provider),
+                                              is_software_rendering);
 }
 
 //------------------------------------------------------------------------------
 
 blink::WebGraphicsContext3DProvider*
 RendererBlinkPlatformImpl::createSharedOffscreenGraphicsContext3DProvider() {
+  auto* thread = RenderThreadImpl::current();
+
   scoped_refptr<ContextProviderCommandBuffer> provider =
-      RenderThreadImpl::current()->SharedMainThreadContextProvider();
+      thread->SharedMainThreadContextProvider();
   if (!provider)
     return nullptr;
-  return new WebGraphicsContext3DProviderImpl(std::move(provider));
+
+  scoped_refptr<gpu::GpuChannelHost> host = thread->EstablishGpuChannelSync();
+  // This shouldn't normally fail because we just got |provider|. But the
+  // channel can become lost on the IO thread since then. It is important that
+  // this happens after getting |provider|. In the case that this GpuChannelHost
+  // is not the same one backing |provider|, the context behind the |provider|
+  // will be already lost/dead on arrival, so the value we get for
+  // |is_software_rendering| will never be wrong.

[piman, 2016/08/22 22:39:51]

Alternatively, we could grab the host from |provider|, to make sure everything
is consistent.

+  if (!host)
+    return nullptr;
+
+  bool is_software_rendering = host->gpu_info().software_rendering;
+
+  return new WebGraphicsContext3DProviderImpl(std::move(provider),
+                                              is_software_rendering);
 }
 
 //------------------------------------------------------------------------------
 
 std::unique_ptr<cc::SharedBitmap>
 RendererBlinkPlatformImpl::allocateSharedBitmap(const blink::WebSize& size) {
   return ChildThreadImpl::current()
       ->shared_bitmap_manager()
       ->AllocateSharedBitmap(gfx::Size(size.width, size.height));
 }
@@ skipping 186 matching lines @@
   return &trial_token_validator_;
 }
 
 void RendererBlinkPlatformImpl::workerContextCreated(
     const v8::Local<v8::Context>& worker) {
   GetContentClient()->renderer()->DidInitializeWorkerContextOnWorkerThread(
       worker);
 }
 
 }  // namespace content