Fix null heap profiler tag for allocations

mojo/public/cpp/bindings/lib/connector.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "mojo/public/cpp/bindings/connector.h"
 
 #include <stdint.h>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 200 matching lines @@
   }
   ReadAllAvailableMessages();
   // At this point, this object might have been deleted. Return.
 }
 
 void Connector::WaitToReadMore() {
   CHECK(!paused_);
   DCHECK(!handle_watcher_);
 
   handle_watcher_.reset(new Watcher(FROM_HERE, task_runner_));
-  handle_watcher_->set_heap_profiler_tag(heap_profiler_tag_);
+  if (heap_profiler_tag_)
+    handle_watcher_->set_heap_profiler_tag(heap_profiler_tag_);
   MojoResult rv = handle_watcher_->Start(
       message_pipe_.get(), MOJO_HANDLE_SIGNAL_READABLE,
       base::Bind(&Connector::OnWatcherHandleReady, base::Unretained(this)));
 
   if (rv != MOJO_RESULT_OK) {
     // If the watch failed because the handle is invalid or its conditions can
     // no longer be met, we signal the error asynchronously to avoid reentry.
     task_runner_->PostTask(
         FROM_HERE,
         base::Bind(&Connector::OnWatcherHandleReady, weak_self_, rv));
@@ skipping 101 matching lines @@
 void Connector::EnsureSyncWatcherExists() {
   if (sync_watcher_)
     return;
   sync_watcher_.reset(new SyncHandleWatcher(
       message_pipe_.get(), MOJO_HANDLE_SIGNAL_READABLE,
       base::Bind(&Connector::OnSyncHandleWatcherHandleReady,
                  base::Unretained(this))));
 }
 
 }  // namespace mojo