Remove the browser shared context from the compositor share group.

Everything goes through mailboxes when used with this context.

R=piman@chromium.org
BUG=584497

Review URL: https://codereview.chromium.org/1898423005

Cr-Commit-Position: refs/heads/master@{#388618}

content/browser/compositor/gpu_process_transport_factory.cc

@@ -93,7 +93,8 @@ const int kNumRetriesBeforeSoftwareFallback = 4;
 
 std::unique_ptr<content::WebGraphicsContext3DCommandBufferImpl>
 CreateContextCommon(scoped_refptr<gpu::GpuChannelHost> gpu_channel_host,
-                    gpu::SurfaceHandle surface_handle) {
+                    gpu::SurfaceHandle surface_handle,
+                    bool share_resources) {
   DCHECK(
       content::GpuDataManagerImpl::GetInstance()->CanUseGpuBrowserCompositor());
   DCHECK(gpu_channel_host);
@@ -119,7 +120,6 @@ CreateContextCommon(scoped_refptr<gpu::GpuChannelHost> gpu_channel_host,
   attributes.bind_generates_resource = false;
   attributes.lose_context_when_out_of_memory = true;
 
-  bool share_resources = true;
   bool automatic_flushes = false;
 
   GURL url("chrome://gpu/GpuProcessTransportFactory::CreateContextCommon");
@@ -343,8 +343,10 @@ void GpuProcessTransportFactory::EstablishedGpuChannel(
 
       // This context is used for both the browser compositor and the display
       // compositor.
+      constexpr bool share_resources = true;
       context_provider = new ContextProviderCommandBuffer(
-          CreateContextCommon(gpu_channel_host, surface_handle),
+          CreateContextCommon(gpu_channel_host, surface_handle,
+                              share_resources),
           gpu::SharedMemoryLimits(), DISPLAY_COMPOSITOR_ONSCREEN_CONTEXT);
       if (!context_provider->BindToCurrentThread())
         context_provider = nullptr;
@@ -352,7 +354,7 @@ void GpuProcessTransportFactory::EstablishedGpuChannel(
       if (!shared_worker_context_provider_) {
         shared_worker_context_provider_ = new ContextProviderCommandBuffer(
             CreateContextCommon(std::move(gpu_channel_host),
-                                gpu::kNullSurfaceHandle),
+                                gpu::kNullSurfaceHandle, share_resources),
             gpu::SharedMemoryLimits(), BROWSER_WORKER_CONTEXT);
         if (shared_worker_context_provider_->BindToCurrentThread())
           shared_worker_context_provider_->SetupLock();
@@ -656,8 +658,10 @@ GpuProcessTransportFactory::SharedMainThreadContextProvider() {
 
   // We need a separate context from the compositor's so that skia and gl_helper
   // don't step on each other.
+  bool share_resources = false;
   shared_main_thread_contexts_ = new ContextProviderCommandBuffer(
-      CreateContextCommon(std::move(gpu_channel_host), gpu::kNullSurfaceHandle),
+      CreateContextCommon(std::move(gpu_channel_host), gpu::kNullSurfaceHandle,
+                          share_resources),
       gpu::SharedMemoryLimits(), BROWSER_OFFSCREEN_MAINTHREAD_CONTEXT);
   shared_main_thread_contexts_->SetLostContextCallback(base::Bind(
       &GpuProcessTransportFactory::OnLostMainThreadSharedContextInsideCallback,