Re-land: cc: Implement shared worker contexts.

content/common/gpu/gpu_channel.cc

Index: content/common/gpu/gpu_channel.cc
diff --git a/content/common/gpu/gpu_channel.cc b/content/common/gpu/gpu_channel.cc
index 7ebd553495ffca7c3e2ff1194c1b5f6910f6a037..4252523d86347dab7d185ab0aff3b2b22b4fb7e4 100644
--- a/content/common/gpu/gpu_channel.cc
+++ b/content/common/gpu/gpu_channel.cc
@@ -70,6 +70,15 @@ const int64 kStopPreemptThresholdMs = kVsyncIntervalMs;
 
 const uint32_t kOutOfOrderNumber = static_cast<uint32_t>(-1);
 
+// Virtualize contexts by defualt on OS X to prevent performance regressions
+// when enabling FCM.
+// http://crbug.com/180463
+#if defined(OS_MACOSX)
+const bool kUseVirtualizedGLContext = true;
+#else
+const bool kUseVirtualizedGLContext = false;
+#endif
+
 }  // anonymous namespace
 
 struct GpuChannelMessage {
@@ -765,20 +774,12 @@ CreateCommandBufferResult GpuChannel::CreateViewCommandBuffer(
     return CREATE_COMMAND_BUFFER_FAILED;
   }
 
-  // Virtualize compositor contexts on OS X to prevent performance regressions
-  // when enabling FCM.
-  // http://crbug.com/180463
-  bool use_virtualized_gl_context = false;
-#if defined(OS_MACOSX)
-  use_virtualized_gl_context = true;
-#endif
-
   scoped_ptr<GpuCommandBufferStub> stub(new GpuCommandBufferStub(
       this, task_runner_.get(), share_group, window, mailbox_manager_.get(),
       subscription_ref_set_.get(), pending_valuebuffer_state_.get(),
       gfx::Size(), disallowed_features_, init_params.attribs,
-      init_params.gpu_preference, use_virtualized_gl_context, stream_id,
-      route_id, surface_id, watchdog_, software_, init_params.active_url));
+      init_params.gpu_preference, kUseVirtualizedGLContext, stream_id, route_id,
+      surface_id, watchdog_, software_, init_params.active_url));
 
   if (preempted_flag_.get())
     stub->SetPreemptByFlag(preempted_flag_);
@@ -1018,7 +1019,7 @@ void GpuChannel::OnCreateOffscreenCommandBuffer(
       this, task_runner_.get(), share_group, gfx::GLSurfaceHandle(),
       mailbox_manager_.get(), subscription_ref_set_.get(),
       pending_valuebuffer_state_.get(), size, disallowed_features_,
-      init_params.attribs, init_params.gpu_preference, false,
+      init_params.attribs, init_params.gpu_preference, kUseVirtualizedGLContext,

[reveman, 2015/09/18 14:51:35]

Not sure exactly why non-virtualized contexts are causing drawing artifacts on
some mac machines when using GPU raster but we probably want to virtualize these
worker contexts for performance reasons anyhow. Do we need to limit this to
worker contexts or is it ok to virtualize all offscreen contexts like I'm doing
in this patch?

[ccameron, 2015/09/18 20:18:53]

When we initially switched to virtualized contexts, we virtualized only
compositor contexts because only they were causing problems WRT creating too
many GL contexts.

I have any good reason to keep doing things this way (kbr may have thoughts on
the issue, though). It may be wise to make this change in a separate patch, to
isolate failures / separate moving parts.

       init_params.stream_id, route_id, 0, watchdog_, software_,
       init_params.active_url));