cros: Allow user to configure note taking app in md-settings.

chrome/browser/ui/webui/settings/chromeos/device_stylus_handler.cc

+// Copyright 2017 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/ui/webui/settings/chromeos/device_stylus_handler.h"
+
+#include "chrome/browser/profiles/profile.h"
+
+namespace chromeos {
+namespace settings {
+
+namespace {
+
+// Keys in objects passed to onNoteTakingAppsUpdated.
+constexpr char kAppNameKey[] = "name";
+constexpr char kAppIdKey[] = "value";
+constexpr char kAppPreferredKey[] = "preferred";
+
+}  // namespace
+
+StylusHandler::StylusHandler() {
+  NoteTakingHelper::Get()->AddObserver(this);
+}
+
+StylusHandler::~StylusHandler() {
+  NoteTakingHelper::Get()->RemoveObserver(this);
+}
+
+void StylusHandler::RegisterMessages() {
+  DCHECK(web_ui());
+
+  web_ui()->RegisterMessageCallback(
+      "requestNoteTakingApps",
+      base::Bind(&StylusHandler::RequestApps, base::Unretained(this)));
+  web_ui()->RegisterMessageCallback(
+      "setPreferredNoteTakingApp",
+      base::Bind(&StylusHandler::SetPreferredNoteTakingApp,
+                 base::Unretained(this)));
+}
+
+void StylusHandler::OnAvailableNoteTakingAppsUpdated() {
+  UpdateNoteTakingApps();
+}
+
+void StylusHandler::UpdateNoteTakingApps() {
+  bool waiting_for_android = false;
+  note_taking_app_ids_.clear();
+  base::ListValue apps_list;
+
+  NoteTakingHelper* helper = NoteTakingHelper::Get();
+  if (helper->android_enabled() && !helper->android_apps_received()) {
+    // If Android is enabled but not ready yet, let the JS know so it can
+    // disable the menu and display an explanatory message.
+    waiting_for_android = true;
+  } else {
+    for (const NoteTakingAppInfo& info :
+         NoteTakingHelper::Get()->GetAvailableApps(
+             Profile::FromWebUI(web_ui()))) {

[stevenjb, 2017/01/19 17:48:53]

nit: This might be a little more clear with:
auto available_aps =
NoteTakingHelper::Get()->GetAvailableApps(Profile::FromWebUI(web_ui()))
above.

[jdufault, 2017/01/25 00:52:22]

Done.

+      auto dict = base::MakeUnique<base::DictionaryValue>();
+      dict->SetString(kAppNameKey, info.name);
+      dict->SetString(kAppIdKey, info.app_id);
+      dict->SetBoolean(kAppPreferredKey, info.preferred);
+      apps_list.Append(std::move(dict));
+
+      note_taking_app_ids_.insert(info.app_id);
+    }
+  }
+
+  CallJavascriptFunction(
+      "cr.webUIListenerCallback", base::StringValue("onNoteTakingAppsUpdated"),
+      apps_list, base::FundamentalValue(waiting_for_android));
+}
+
+void StylusHandler::RequestApps(const base::ListValue* unused_args) {
+  AllowJavascript();
+  UpdateNoteTakingApps();
+}
+
+void StylusHandler::SetPreferredNoteTakingApp(const base::ListValue* args) {
+  std::string app_id;
+  CHECK(args->GetString(0, &app_id));
+
+  // Sanity check: make sure that the ID we got back from WebUI is in the
+  // currently-available set.
+  if (!note_taking_app_ids_.count(app_id)) {
+    LOG(ERROR) << "Got unknown note-taking-app ID \"" << app_id << "\"";
+    return;
+  }
+
+  NoteTakingHelper::Get()->SetPreferredApp(Profile::FromWebUI(web_ui()),

[Daniel Erat, 2017/01/19 00:50:05]

since we discussed it before: it ended up making sense to keep this method?

[jdufault, 2017/01/25 00:52:22]

Yea, given the nature of how preferred values are updated (ie, not updated if
the user does not actively select a different value) I figured it would be
better to make the pref handling explicit.

+                                           app_id);
+}
+
+}  // namespace settings
+}  // namespace chromeos