Remove BrowserThread-specific implementation of MessageLoopProxy.

content/public/browser/browser_thread.h

Index: content/public/browser/browser_thread.h
diff --git a/content/public/browser/browser_thread.h b/content/public/browser/browser_thread.h
index 0ac582b7c00221da876dd8729c2a6edf23032c61..32f9427b826a644527be01c7c889d59841393f32 100644
--- a/content/public/browser/browser_thread.h
+++ b/content/public/browser/browser_thread.h
@@ -151,8 +151,11 @@ class CONTENT_EXPORT BrowserThread {
   static bool DeleteSoon(ID identifier,
                          const tracked_objects::Location& from_here,
                          const T* object) {
-    return GetMessageLoopProxyForThread(identifier)->DeleteSoon(
-        from_here, object);
+    scoped_refptr<base::MessageLoopProxy> message_loop_proxy =
+        GetMessageLoopProxyForThread(identifier);
+    if (!message_loop_proxy)
+      return false;
+    return message_loop_proxy->DeleteSoon(from_here, object);
   }
 
   template <class T>