Re-land: cc: Implement shared worker contexts.

content/renderer/render_thread_impl.cc

Index: content/renderer/render_thread_impl.cc
diff --git a/content/renderer/render_thread_impl.cc b/content/renderer/render_thread_impl.cc
index db40b5af28e9f0cdee38e39c246d4d9e1ff14867..674a190e86d0ee4745070414f654109a016d3856 100644
--- a/content/renderer/render_thread_impl.cc
+++ b/content/renderer/render_thread_impl.cc
@@ -845,6 +845,7 @@ void RenderThreadImpl::Shutdown() {
   main_thread_compositor_task_runner_ = NULL;
 
   // Context providers must be released prior to destroying the GPU channel.
+  shared_worker_context_provider_ = nullptr;
   gpu_va_context_provider_ = nullptr;
   shared_main_thread_contexts_ = nullptr;
 
@@ -1888,6 +1889,30 @@ base::TaskRunner* RenderThreadImpl::GetWorkerTaskRunner() {
   return raster_worker_pool_.get();
 }
 
+scoped_refptr<ContextProviderCommandBuffer>
+RenderThreadImpl::SharedWorkerContextProvider() {
+  DCHECK(IsMainThread());
+  // Try to reuse existing shared worker context provider.
+  bool shared_worker_context_provider_lost = false;
+  if (shared_worker_context_provider_) {
+    base::AutoLock lock(*shared_worker_context_provider_->GetLock());
+    if (shared_worker_context_provider_->ContextGL()
+            ->GetGraphicsResetStatusKHR() != GL_NO_ERROR) {
+      shared_worker_context_provider_lost = true;
+    }
+  }
+  if (!shared_worker_context_provider_ || shared_worker_context_provider_lost) {
+    shared_worker_context_provider_ = ContextProviderCommandBuffer::Create(
+        CreateOffscreenContext3d(), RENDER_WORKER_CONTEXT);
+    if (shared_worker_context_provider_ &&
+        !shared_worker_context_provider_->BindToCurrentThread())
+      shared_worker_context_provider_ = nullptr;
+    if (shared_worker_context_provider_)
+      shared_worker_context_provider_->SetupLock();
+  }
+  return shared_worker_context_provider_;
+}
+
 void RenderThreadImpl::SampleGamepads(blink::WebGamepads* data) {
   blink_platform_impl_->sampleGamepads(*data);
 }