Make SingleThreadProxy a SchedulerClient

cc/test/test_web_graphics_context_3d.cc

Index: cc/test/test_web_graphics_context_3d.cc
diff --git a/cc/test/test_web_graphics_context_3d.cc b/cc/test/test_web_graphics_context_3d.cc
index 59b7440d63854475fffbdb221a5f27b945adef1a..5f220376798dc9bcc4276f48364d48c175b57328 100644
--- a/cc/test/test_web_graphics_context_3d.cc
+++ b/cc/test/test_web_graphics_context_3d.cc
@@ -443,12 +443,15 @@ void TestWebGraphicsContext3D::loseContextCHROMIUM(GLenum current,
   if (context_lost_)
     return;
   context_lost_ = true;
-  if (!context_lost_callback_.is_null())
-    context_lost_callback_.Run();
 
   for (size_t i = 0; i < shared_contexts_.size(); ++i)
     shared_contexts_[i]->loseContextCHROMIUM(current, other);
   shared_contexts_.clear();
+
+  // In the single thread case, this could cause the context to be
+  // synchronously deleted, so do it last.
+  if (!context_lost_callback_.is_null())
+    context_lost_callback_.Run();
 }
 
 void TestWebGraphicsContext3D::finish() {