Add devtools trace events for Timeline EmbedderCallback notification

android_webview/common/devtools_instrumentation.h

 // Copyright 2014 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.
 
 #ifndef ANDROID_WEBVIEW_COMMON_DEVTOOLS_INSTRUMENTATION_H_
 #define ANDROID_WEBVIEW_COMMON_DEVTOOLS_INSTRUMENTATION_H_
 
 #include "base/debug/trace_event.h"
 
 namespace android_webview {
 namespace devtools_instrumentation {
 
 namespace internal {
-const char kCategory[] = "Java,devtools";
+const char kCategory[] = "Java,devtools,disabled-by-default-devtools.timeline";
 const char kEmbedderCallback[] = "EmbedderCallback";
 const char kCallbackNameArgument[] = "callbackName";
 }  // namespace internal
 
 class ScopedEmbedderCallbackTask {
  public:
   ScopedEmbedderCallbackTask(const char* callback_name) {
     TRACE_EVENT_BEGIN1(internal::kCategory,
                        internal::kEmbedderCallback,
                        internal::kCallbackNameArgument,
                        callback_name);
   }
   ~ScopedEmbedderCallbackTask() {
     TRACE_EVENT_END0(internal::kCategory,
                      internal::kEmbedderCallback);
   }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ScopedEmbedderCallbackTask);
 };
 
 }  // namespace devtools_instrumentation
 }  // namespace android_webview
 
 #endif  // ANDROID_WEBVIEW_COMMON_DEVTOOLS_INSTRUMENTATION_H_