SetNeedsRedraw directly when updating a visible tile.

cc/test/thread_blocker.cc

Index: cc/test/thread_blocker.cc
diff --git a/cc/test/thread_blocker.cc b/cc/test/thread_blocker.cc
new file mode 100644
index 0000000000000000000000000000000000000000..f87ca8fd9c0a4e4367c8e6ec087ab1d1c4082f92
--- /dev/null
+++ b/cc/test/thread_blocker.cc
@@ -0,0 +1,39 @@
+// 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.
+
+#include "cc/test/thread_blocker.h"
+
+#include "base/bind.h"
+
+namespace cc {
+
+ThreadBlocker::ThreadBlocker()
+    : should_delay_(false),
+      waiter_(false /* manual_reset */, false /* initially_signaled */) {
+}
+
+ThreadBlocker::~ThreadBlocker() {
+}
+
+void ThreadBlocker::Wait() {
+  {
+    base::AutoLock lock(lock_);
+    if (!should_delay_)
+      return;
+  }
+  waiter_.Wait();
+}
+
+void ThreadBlocker::BlockWait() {
+  base::AutoLock lock(lock_);
+  should_delay_ = true;
+}
+
+void ThreadBlocker::UnblockWait() {
+  base::AutoLock lock(lock_);
+  should_delay_ = false;
+  waiter_.Signal();
+}
+
+}  // namespace cc