Initial implementation of music manager private API.

chrome/browser/extensions/api/music_manager_private/music_manager_private_api.cc

+// Copyright 2013 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/browser/extensions/api/music_manager_private/music_manager_private_api.h"
+#include "chrome/browser/extensions/api/music_manager_private/device_id.h"
+
+using content::BrowserThread;
+
+namespace extensions {
+
+namespace api {
+
+MusicManagerPrivateGetDeviceIdFunction::
+  MusicManagerPrivateGetDeviceIdFunction() {
+}
+
+MusicManagerPrivateGetDeviceIdFunction::
+  ~MusicManagerPrivateGetDeviceIdFunction() {
+}
+
+bool MusicManagerPrivateGetDeviceIdFunction::RunImpl() {
+  BrowserThread::PostTask(
+      BrowserThread::IO, FROM_HERE,
+      base::Bind(&MusicManagerPrivateGetDeviceIdFunction::ComputeOnIOThread,
+                 this));
+
+  return true;
+}
+
+void  MusicManagerPrivateGetDeviceIdFunction::ComputeOnIOThread() {

[Matt Perry, 2013/05/22 22:19:11]

Why does this need to be done on the IO thread?

[rpaquay, 2013/05/22 23:55:50]

I am not 100% sure. This code is inspired from
DeviceIDFetcher::ComputeOnIOThread in
chrome/browser/renderer_host/pepper/device_id_fetcher.cc, which is run on the IO
thread. The only explanation I have is that we don't want to run this on the UI
thread because the operation may be CPU intensive. There might be other reasons.

[Matt Perry, 2013/05/23 00:01:15]

Could you please doublecheck with the author of that code? If this is
computationally intensive, it's not a good idea to block the IO thread either.
It would be better to put it on a WorkerPool.

[rpaquay, 2013/05/23 19:39:46]

It turns our this computation is not expensive, so we can run the function on
the UI thread. Created new patchset with corresponding change.

+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+
+  std::string salt = this->extension_id();
+  std::string result = device_id::GetDeviceID(salt);
+  bool response;
+  if (result.empty()) {
+    SetError("Device ID API is not supported on this platform.");

[Matt Perry, 2013/05/22 22:19:11]

move this to a constant at the top of the file.

[rpaquay, 2013/05/22 23:55:50]

Done.

+    response = false;
+  } else {
+    SetResult(Value::CreateStringValue(result));
+    response = true;
+  }
+
+  content::BrowserThread::PostTask(content::BrowserThread::IO, FROM_HERE,

[Matt Perry, 2013/05/22 22:19:11]

you want to post this to the UI thread

[rpaquay, 2013/05/22 23:55:50]

Sorry, last minute typo. Done.

+      base::Bind(&MusicManagerPrivateGetDeviceIdFunction::SendResponse,
+                 this,
+                 response));
+}
+
+} // namespace api
+
+} // namespace extensions