Hook up ui::Compositor to Display's BeginFrameSource

components/mus/surfaces/surfaces_context_provider.cc

Index: components/mus/surfaces/surfaces_context_provider.cc
diff --git a/components/mus/surfaces/surfaces_context_provider.cc b/components/mus/surfaces/surfaces_context_provider.cc
index 6995806b6f207026ccd61c8b3ca944150e68e4bb..58ac6668e2b422628c2e1660c3f081218930c144 100644
--- a/components/mus/surfaces/surfaces_context_provider.cc
+++ b/components/mus/surfaces/surfaces_context_provider.cc
@@ -28,14 +28,19 @@ const size_t kDefaultMaxTransferBufferSize = 16 * 1024 * 1024;
 }
 
 SurfacesContextProvider::SurfacesContextProvider(
-    SurfacesContextProviderDelegate* delegate,
     gfx::AcceleratedWidget widget,
     const scoped_refptr<GpuState>& state)
-    : delegate_(delegate), widget_(widget), command_buffer_local_(nullptr) {
+    : delegate_(nullptr), widget_(widget), command_buffer_local_(nullptr) {
   capabilities_.gpu.image = true;
   command_buffer_local_ = new CommandBufferLocal(this, widget_, state);
 }
 
+void SurfacesContextProvider::SetDelegate(
+    SurfacesContextProviderDelegate* delegate) {
+  DCHECK(!delegate_);
+  delegate_ = delegate;
+}
+
 // This is called when we have an accelerated widget.
 bool SurfacesContextProvider::BindToCurrentThread() {
   // SurfacesContextProvider should always live on the same thread as the