Re-land: cc: Use worker context for one-copy tile initialization.

cc/output/output_surface.cc

Index: cc/output/output_surface.cc
diff --git a/cc/output/output_surface.cc b/cc/output/output_surface.cc
index a597a87d8456bc65f3ce763d469db9e7e776ed7f..0786d660d4a58a3e24c03dabc3411f9d3e08cd9a 100644
--- a/cc/output/output_surface.cc
+++ b/cc/output/output_surface.cc
@@ -107,10 +107,6 @@ OutputSurface::~OutputSurface() {
     context_provider_->SetMemoryPolicyChangedCallback(
         ContextProvider::MemoryPolicyChangedCallback());
   }
-  if (worker_context_provider_.get()) {
-    worker_context_provider_->SetLostContextCallback(
-        ContextProvider::LostContextCallback());
-  }
 }
 
 bool OutputSurface::HasExternalStencilTest() const {
@@ -134,14 +130,8 @@ bool OutputSurface::BindToClient(OutputSurfaceClient* client) {
 
   if (success && worker_context_provider_.get()) {
     success = worker_context_provider_->BindToCurrentThread();
-    if (success) {
+    if (success)
       worker_context_provider_->SetupLock();
-      // The destructor resets the context lost callback, so base::Unretained
-      // is safe, as long as the worker threads stop using the context before
-      // the output surface is destroyed.
-      worker_context_provider_->SetLostContextCallback(base::Bind(
-          &OutputSurface::DidLoseOutputSurface, base::Unretained(this)));
-    }
   }
 
   if (!success)
@@ -217,11 +207,7 @@ void OutputSurface::SetWorkerContextShouldAggressivelyFreeResources(
                "OutputSurface::SetWorkerContextShouldAggressivelyFreeResources",
                "aggressively_free_resources", aggressively_free_resources);
   if (auto* context_provider = worker_context_provider()) {
-    // The context lock must be held while accessing the worker context.
-    base::AutoLock context_lock(*context_provider->GetLock());
-
-    // Allow context to bind to current thread.
-    context_provider->DetachFromThread();
+    ContextProvider::ScopedContextLock scoped_context(context_provider);
 
     if (aggressively_free_resources) {
       context_provider->DeleteCachedResources();
@@ -231,9 +217,6 @@ void OutputSurface::SetWorkerContextShouldAggressivelyFreeResources(
       context_support->SetAggressivelyFreeResources(
           aggressively_free_resources);
     }
-
-    // Allow context to bind to other threads.
-    context_provider->DetachFromThread();
   }
 }