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 c5f950f580eacb213905ee6593dc571ea915bff3..76cd19dc191ff8624982205a2d93b573b0058ecb 100644
--- a/ui/compositor/test/in_process_context_provider.cc
+++ b/ui/compositor/test/in_process_context_provider.cc
@@ -122,6 +122,10 @@ bool InProcessContextProvider::BindToCurrentThread() {
   return true;
 }
 
+void InProcessContextProvider::DetachFromThread() {
+  context_thread_checker_.DetachFromThread();
+}
+
 cc::ContextProvider::Capabilities
 InProcessContextProvider::ContextCapabilities() {
   DCHECK(context_thread_checker_.CalledOnValidThread());