[WebMIDI] Add "use-android-midi-api" flag for Android M+ devices.

content/browser/browser_main_loop.cc

 // Copyright (c) 2012 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 "content/browser/browser_main_loop.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/location.h"
 #include "base/logging.h"
@@ skipping 1143 matching lines @@
       BrowserGpuMemoryBufferManager::current(), io_thread_->task_runner());
 
   {
     TRACE_EVENT0("startup", "BrowserThreadsStarted::Subsystem:AudioMan");
     audio_manager_.reset(media::AudioManager::CreateWithHangTimer(
         MediaInternals::GetInstance(), io_thread_->task_runner()));
   }
 
   {
     TRACE_EVENT0("startup", "BrowserThreadsStarted::Subsystem:MidiManager");
-    midi_manager_.reset(media::midi::MidiManager::Create());
+    media::midi::MidiManager::CreationOptions options;

[Takashi Toyoshima, 2015/08/12 04:39:47]

I prefer to use
base::CommandLine::ForCurrentProcess()->HasSwitch(switches::kUseAndroidMidiApi)
inside MidiManager(Android) so that we do not need to touch this file, and have
options for constructors.

[yhirano, 2015/08/12 05:37:05]

Done.

+#if defined(OS_ANDROID)
+    options.set_use_native_midi_api(
+        parsed_command_line_.HasSwitch(switches::kUseAndroidMidiApi));
+#endif
+    midi_manager_.reset(media::midi::MidiManager::Create(options));
   }
 
 #if defined(OS_LINUX) && defined(USE_UDEV)
   device_monitor_linux_.reset(new DeviceMonitorLinux());
 #elif defined(OS_MACOSX)
   device_monitor_mac_.reset(new DeviceMonitorMac());
 #endif
 
 #if defined(OS_WIN)
   UMA_HISTOGRAM_BOOLEAN("Windows.Win32kRendererLockdown",
@@ skipping 185 matching lines @@
   DCHECK(is_tracing_startup_);
 
   is_tracing_startup_ = false;
   TracingController::GetInstance()->DisableRecording(
       TracingController::CreateFileSink(
           startup_trace_file_,
           base::Bind(OnStoppedStartupTracing, startup_trace_file_)));
 }
 
 }  // namespace content