Tag some of Mojo heap allocations for the heap profiler.

mojo/android/system/watcher_impl.cc

 // Copyright 2016 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/android/system/watcher_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include "base/android/base_jni_registrar.h"
@@ skipping 10 matching lines @@
 namespace mojo {
 namespace android {
 
 using base::android::JavaParamRef;
 
 namespace {
 
 class WatcherWithMessageLoopObserver
     : public base::MessageLoop::DestructionObserver {
  public:
-  WatcherWithMessageLoopObserver() {}
+  WatcherWithMessageLoopObserver() : watcher_(FROM_HERE) {}
 
   ~WatcherWithMessageLoopObserver() override { StopObservingIfNecessary(); }
 
   jint Start(JNIEnv* env,
              const JavaParamRef<jobject>& jcaller,
              jint mojo_handle,
              jint signals) {
     if (!is_observing_) {
       is_observing_ = true;
       base::MessageLoop::current()->AddDestructionObserver(this);
@@ skipping 84 matching lines @@
                    jlong watcher_ptr) {
   delete reinterpret_cast<WatcherWithMessageLoopObserver*>(watcher_ptr);
 }
 
 bool RegisterWatcherImpl(JNIEnv* env) {
   return RegisterNativesImpl(env);
 }
 
 }  // namespace android
 }  // namespace mojo