mojo: Use TYPE_DEFAULT message-loop for browser-tests.

chrome/app/mash/mash_runner.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 "chrome/app/mash/mash_runner.h"
 
 #include "base/at_exit.h"
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/debug/debugger.h"
@@ skipping 108 matching lines @@
 }
 
 void MashRunner::RunChild() {
   base::i18n::InitializeICU();
   shell::ChildProcessMainWithCallback(
       base::Bind(&MashRunner::StartChildApp, base::Unretained(this)));
 }
 
 void MashRunner::StartChildApp(
     shell::mojom::ServiceRequest service_request) {
-  // TODO(sky): use MessagePumpMojo.
+  // TODO(sad): Normally, this would be a TYPE_DEFAULT message loop. However,
+  // TYPE_UI is needed for mojo:ui. But it is not known whether the child app is
+  // going to be mojo:ui at this point. So always create a TYPE_UI message loop
+  // for now.
   base::MessageLoop message_loop(base::MessageLoop::TYPE_UI);
   service_.reset(new mash::MashPackagedService);
   service_->set_context(base::MakeUnique<shell::ServiceContext>(
       service_.get(), std::move(service_request)));
   base::RunLoop().Run();
 }
 
 int MashMain() {
 #if defined(OS_WIN)
   base::RouteStdioToConsole(false);
 #endif
   // TODO(sky): wire this up correctly.
   logging::LoggingSettings settings;
   settings.logging_dest = logging::LOG_TO_SYSTEM_DEBUG_LOG;
   logging::InitLogging(settings);
   // To view log output with IDs and timestamps use "adb logcat -v threadtime".
   logging::SetLogItems(true,   // Process ID
                        true,   // Thread ID
                        true,   // Timestamp
                        true);  // Tick count
 
-  // TODO(sky): use MessagePumpMojo.
   std::unique_ptr<base::MessageLoop> message_loop;
 #if defined(OS_LINUX)
   base::AtExitManager exit_manager;
 #endif
   if (!IsChild())
     message_loop.reset(new base::MessageLoop(base::MessageLoop::TYPE_UI));
 
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kTraceToConsole)) {
     base::trace_event::TraceConfig trace_config =
         tracing::GetConfigForTraceToConsole();
     base::trace_event::TraceLog::GetInstance()->SetEnabled(
         trace_config,
         base::trace_event::TraceLog::RECORDING_MODE);
   }
 
   MashRunner mash_runner;
   mash_runner.Run();
   return 0;
 }