cc: Dump scheduler and tile manager state when commit is blocked.

cc/base/completion_event.h

Index: cc/base/completion_event.h
diff --git a/cc/base/completion_event.h b/cc/base/completion_event.h
index edee0b78bf0e7bff28b07b878faae6a2ea858cce..0c620db4e72693a19993a16e82f247eec844fb5e 100644
--- a/cc/base/completion_event.h
+++ b/cc/base/completion_event.h
@@ -43,12 +43,18 @@ class CompletionEvent {
     event_.Wait();
   }
 
-  void TimedWait(const base::TimeDelta& max_time) {
+  bool TimedWait(const base::TimeDelta& max_time) {
 #if DCHECK_IS_ON()
     DCHECK(!waited_);
     waited_ = true;
 #endif
-    event_.TimedWait(max_time);
+    base::ThreadRestrictions::ScopedAllowWait allow_wait;
+    if (event_.TimedWait(max_time))
+      return true;
+#if DCHECK_IS_ON()
+    waited_ = false;
+#endif
+    return false;
   }
 
   bool IsSignaled() { return event_.IsSignaled(); }