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

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 a29bb9d27edba4d7ef1f86a27d6a8c8a3c9356a2..858d8c21601fe75870382a84827f1a52a9374a42 100644
--- a/ui/compositor/test/in_process_context_provider.cc
+++ b/ui/compositor/test/in_process_context_provider.cc
@@ -128,6 +128,10 @@ bool InProcessContextProvider::BindToCurrentThread() {
   return true;
 }
 
+void InProcessContextProvider::DetachFromThread() {
+  context_thread_checker_.DetachFromThread();
+}
+
 cc::ContextProvider::Capabilities
 InProcessContextProvider::ContextCapabilities() {
   DCHECK(context_thread_checker_.CalledOnValidThread());