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..d13d7d7b6ede75d1ccd32ca3e043a5ac11a16a30 100644
--- a/base/threading/thread.h
+++ b/base/threading/thread.h
@@ -245,6 +245,12 @@ 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.

[gab, 2017/05/04 18:11:58]

TODO(robliao): remove this when it no longer needs to be temporarily exposed for
http://crbug.com/717380.

...so its usage doesn't spread like wildfire and we can actually remove it when
we fix the current use case.

[robliao, 2017/05/04 19:01:49]

Done.

+  PlatformThreadHandle GetThreadHandle() const;
+
   // Returns true if the thread has been started, and not yet stopped.
   bool IsRunning() const;