Let Dart code running in Sky add events to the trace timeline

sky/engine/core/script/dart_controller.cc

 // Copyright 2015 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 "sky/engine/config.h"
 #include "sky/engine/core/script/dart_controller.h"
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/single_thread_task_runner.h"
@@ skipping 194 matching lines @@
     Builtin::SetNativeResolver(Builtin::kMojoInternalLibrary);
   }
 
   Dart_ExitIsolate();
 
   CHECK(Dart_IsolateMakeRunnable(isolate));
   return isolate;
 }
 
 static void CallHandleMessage(base::WeakPtr<DartState> dart_state) {
+  TRACE_EVENT0("sky", "CallHandleMessage");
+
   if (!dart_state)
     return;
 
   DartIsolateScope scope(dart_state->isolate());
   DartApiScope api_scope;
   LogIfError(Dart_HandleMessage());
 }
 
 static void MessageNotifyCallback(Dart_Isolate dest_isolate) {
   DCHECK(Platform::current());
@@ skipping 78 matching lines @@
 
   CHECK(Dart_SetVMFlags(argc, argv));
   CHECK(Dart_Initialize(IsolateCreateCallback,
                         nullptr,  // Isolate interrupt callback.
                         UnhandledExceptionCallback, IsolateShutdownCallback,
                         // File IO callbacks.
                         nullptr, nullptr, nullptr, nullptr, nullptr));
 }
 
 } // namespace blink