Show Media Router toolbar icon ephemerally for MR dialogs

chrome/browser/ui/toolbar/media_router_action_controller.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/browser/ui/toolbar/media_router_action_controller.h"
 
 #include "chrome/browser/media/router/media_router_factory.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/toolbar/component_toolbar_actions_factory.h"
 #include "chrome/browser/ui/toolbar/toolbar_actions_model.h"
 #include "chrome/common/pref_names.h"
 
 MediaRouterActionController::MediaRouterActionController(Profile* profile)
     : MediaRouterActionController(
           profile,
           media_router::MediaRouterFactory::GetApiForBrowserContext(profile),
           ToolbarActionsModel::Get(profile),
-          ToolbarActionsModel::Get(profile)->component_migration_helper()) {}
+          ToolbarActionsModel::Get(profile)->component_migration_helper()) {
+  DCHECK(component_action_delegate_);
+  DCHECK(component_migration_helper_);
+}
 
 MediaRouterActionController::~MediaRouterActionController() {
+  DCHECK_EQ(dialog_count_, 0u);
   UnregisterObserver();  // media_router::IssuesObserver.
 }
 
 void MediaRouterActionController::OnIssueUpdated(
     const media_router::Issue* issue) {
   has_issue_ = issue != nullptr;
   MaybeAddOrRemoveAction();
 }
 
 void MediaRouterActionController::OnRoutesUpdated(
     const std::vector<media_router::MediaRoute>& routes,
     const std::vector<media_router::MediaRoute::Id>& joinable_route_ids) {
   has_local_display_route_ =
       std::find_if(routes.begin(), routes.end(),
                    [](const media_router::MediaRoute& route) {
                      return route.is_local() && route.for_display();
                    }) != routes.end();
 
   MaybeAddOrRemoveAction();
 }
 
+void MediaRouterActionController::OnDialogShown() {
+  dialog_count_++;
+  MaybeAddOrRemoveAction();
+}
+
+void MediaRouterActionController::OnDialogHidden() {
+  DCHECK_GT(dialog_count_, 0u);
+  if (dialog_count_)
+    dialog_count_--;
+  MaybeAddOrRemoveAction();
+}
+
 MediaRouterActionController::MediaRouterActionController(
     Profile* profile,
     media_router::MediaRouter* router,
     extensions::ComponentMigrationHelper::ComponentActionDelegate*
         component_action_delegate,
     extensions::ComponentMigrationHelper* component_migration_helper)
     : media_router::IssuesObserver(router),
       media_router::MediaRoutesObserver(router),
       profile_(profile),
       component_action_delegate_(component_action_delegate),
       component_migration_helper_(component_migration_helper) {
   DCHECK(profile_);
-  DCHECK(component_action_delegate_);
   RegisterObserver();  // media_router::IssuesObserver.
   pref_change_registrar_.Init(profile->GetPrefs());
   pref_change_registrar_.Add(
       prefs::kToolbarMigratedComponentActionStatus,
       base::Bind(&MediaRouterActionController::MaybeAddOrRemoveAction,
                  base::Unretained(this)));
 }
 
 void MediaRouterActionController::MaybeAddOrRemoveAction() {
   if (ShouldEnableAction()) {
     if (!component_action_delegate_->HasComponentAction(
-            ComponentToolbarActionsFactory::kMediaRouterActionId))
+            ComponentToolbarActionsFactory::kMediaRouterActionId)) {
       component_action_delegate_->AddComponentAction(
           ComponentToolbarActionsFactory::kMediaRouterActionId);
+    }
   } else if (component_action_delegate_->HasComponentAction(
                  ComponentToolbarActionsFactory::kMediaRouterActionId)) {
     component_action_delegate_->RemoveComponentAction(
         ComponentToolbarActionsFactory::kMediaRouterActionId);
   }
 }
 
 bool MediaRouterActionController::ShouldEnableAction() const {
-  return has_local_display_route_ || has_issue_ ||
+  return has_local_display_route_ || has_issue_ || dialog_count_ ||
          component_migration_helper_->GetComponentActionPref(
              ComponentToolbarActionsFactory::kMediaRouterActionId);
 }