cc: Implement shared worker contexts.

ui/compositor/test/in_process_context_provider.cc

Index: ui/compositor/test/in_process_context_provider.cc
diff --git a/ui/compositor/test/in_process_context_provider.cc b/ui/compositor/test/in_process_context_provider.cc
index 76cd19dc191ff8624982205a2d93b573b0058ecb..ceef9676546d05a07fe8d37988ee4b97942bd365 100644
--- a/ui/compositor/test/in_process_context_provider.cc
+++ b/ui/compositor/test/in_process_context_provider.cc
@@ -85,9 +85,13 @@ InProcessContextProvider::InProcessContextProvider(
   context_thread_checker_.DetachFromThread();
 }
 
-InProcessContextProvider::~InProcessContextProvider() {
-  DCHECK(main_thread_checker_.CalledOnValidThread() ||
-         context_thread_checker_.CalledOnValidThread());
+InProcessContextProvider::~InProcessContextProvider() {}
+
+void InProcessContextProvider::Destroy() {
+  base::AutoLock lock(destroyed_lock_);
+  if (context_)
+    context_->SetContextLostCallback(base::Closure());
+  destroyed_ = true;
 }
 
 bool InProcessContextProvider::BindToCurrentThread() {