Bug 923486, part 2 - Define NS_IsMainThread out-of-line in ASAN builds. r=ehsan

xpcom/glue/MainThreadUtils.h

@@ -29,14 +29,14 @@ bool NS_IsMainThread();
 extern NS_TLS mozilla::threads::ID gTLSThreadID;
 #ifdef MOZ_ASAN
 // Temporary workaround, see bug 895845
-MOZ_ASAN_BLACKLIST static
+MOZ_ASAN_BLACKLIST bool NS_IsMainThread();
 #else
 inline
-#endif
 bool NS_IsMainThread()
 {
   return gTLSThreadID == mozilla::threads::Main;
 }
+#endif
 #else
 /**
  * Test to see if the current thread is the main thread.

xpcom/glue/nsThreadUtils.cpp

@@ -122,7 +122,15 @@ NS_IsMainThread()
   return TlsGetValue(gTLSThreadIDIndex) == (void*) mozilla::threads::Main;
 }
 #elif defined(MOZILLA_INTERNAL_API) && defined(NS_TLS)
+#ifdef MOZ_ASAN
+// Temporary workaround, see bug 895845
+bool NS_IsMainThread()
+{
+  return gTLSThreadID == mozilla::threads::Main;
+}
+#else
 // NS_IsMainThread() is defined inline in MainThreadUtils.h
+#endif
 #else
 #ifdef MOZILLA_INTERNAL_API
 bool NS_IsMainThread()