Exempt the Service Thread from BLOCK_SHUTDOWN DCHECKs

base/threading/thread.h

Index: base/threading/thread.h
diff --git a/base/threading/thread.h b/base/threading/thread.h
index 2db69c2148019ad3c666d001524344dc45ce1ce2..8237a23a57c6e2e6092314140be2a2054b03e577 100644
--- a/base/threading/thread.h
+++ b/base/threading/thread.h
@@ -245,6 +245,15 @@ class BASE_EXPORT Thread : PlatformThread::Delegate {
   // This method is thread-safe.
   PlatformThreadId GetThreadId() const;
 
+  // Returns the current thread handle. If called before Start*() returns or
+  // after Stop() returns, an empty thread handle will be returned.
+  //
+  // This method is thread-safe.
+  //
+  // TODO(robliao): Remove this when it no longer needs to be temporarily
+  // exposed for http://crbug.com/717380.
+  PlatformThreadHandle GetThreadHandle() const;
+
   // Returns true if the thread has been started, and not yet stopped.
   bool IsRunning() const;