Exempt the Service Thread from BLOCK_SHUTDOWN DCHECKs

base/threading/thread.cc

Index: base/threading/thread.cc
diff --git a/base/threading/thread.cc b/base/threading/thread.cc
index 75c911b7f87dced1d2b9695a86af4f8efc2f1aff..183f27e0a1d324b0b2a2e27fe3850d860a5eb901 100644
--- a/base/threading/thread.cc
+++ b/base/threading/thread.cc
@@ -225,6 +225,11 @@ PlatformThreadId Thread::GetThreadId() const {
   return id_;
 }
 
+PlatformThreadHandle Thread::GetThreadHandle() const {
+  AutoLock lock(thread_lock_);
+  return thread_;
+}
+
 bool Thread::IsRunning() const {
   // TODO(gab): Fix improper usage of this API (http://crbug.com/629139) and
   // enable this check.