SetNeedsRedraw directly when updating a visible tile.

cc/test/thread_blocker.h

Index: cc/test/thread_blocker.h
diff --git a/cc/test/thread_blocker.h b/cc/test/thread_blocker.h
new file mode 100644
index 0000000000000000000000000000000000000000..d7ab0b829cf720d3b72f665498ab98b68c6a5a3f
--- /dev/null
+++ b/cc/test/thread_blocker.h
@@ -0,0 +1,42 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CC_TEST_THREAD_BLOCKER_H_
+#define CC_TEST_THREAD_BLOCKER_H_
+
+#include "base/synchronization/lock.h"
+#include "base/synchronization/waitable_event.h"
+
+namespace cc {
+
+// This class will block inside the Wait() function after BlockWait() has been
+// called until UnblockWait() is called. Because Wait() blocks, the
+// UnblockWait() call must be done from another thread, so this class is safe to
+// use on multiple threads.
+class ThreadBlocker {
+ public:
+  ThreadBlocker();
+  ~ThreadBlocker();
+
+  // This will block if BlockWait() has been called until UnblockWait() is
+  // called.
+  void Wait();
+
+  // Makes future calls to Wait() block.
+  void BlockWait();
+  // Unblocks any current calls to Wait() and prevents future calls from
+  // blocking.
+  void UnblockWait();
+
+ private:
+  base::Lock lock_;
+  bool should_delay_;
+  base::WaitableEvent waiter_;
+
+  DISALLOW_COPY_AND_ASSIGN(ThreadBlocker);
+};
+
+}  // namespace cc
+
+#endif  // CC_TEST_THREAD_BLOCKER_H_