chromeos: Fix regression in Android note-taking app list.

Fix a bug where the note-taking app list spins forever due
to intent filter changes not being observed for newly-added
profiles.

Bug: 748763
Change-Id: I094f989ef986d8a8eaf2f2492d46a3c18ea73159
Reviewed-on: https://chromium-review.googlesource.com/594893Reviewed-by: Hidehiko Abe <hidehiko@chromium.org>
Commit-Queue: Dan Erat <derat@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491201}

chrome/browser/chromeos/note_taking_helper.cc

@@ -549,6 +549,10 @@ void NoteTakingHelper::Observe(int type,
     for (Observer& observer : observers_)
       observer.OnAvailableNoteTakingAppsUpdated();
   }
+
+  auto* bridge = arc::ArcIntentHelperBridge::GetForBrowserContext(profile);
+  if (bridge)
+    bridge->AddObserver(this);
 }
 
 void NoteTakingHelper::OnExtensionLoaded(

chrome/browser/chromeos/note_taking_helper_unittest.cc

@@ -875,6 +875,10 @@ TEST_P(NoteTakingHelperTest, AddProfileWithPlayStoreEnabled) {
   EXPECT_FALSE(helper()->android_apps_received());
   EXPECT_EQ(1, observer.num_updates());
 
+  // TODO(derat|hidehiko): Check that NoteTakingHelper adds itself as an
+  // observer of the ArcIntentHelperBridge corresponding to the new profile:
+  // https://crbug.com/748763
+
   // Notification of updated intent filters should result in the apps being
   // refreshed.
   helper()->OnIntentFiltersUpdated();

components/arc/intent_helper/arc_intent_helper_bridge.cc

@@ -156,6 +156,11 @@ void ArcIntentHelperBridge::RemoveObserver(ArcIntentHelperObserver* observer) {
   observer_list_.RemoveObserver(observer);
 }
 
+bool ArcIntentHelperBridge::HasObserver(
+    ArcIntentHelperObserver* observer) const {
+  return observer_list_.HasObserver(observer);
+}
+
 std::unique_ptr<ash::LinkHandlerModel> ArcIntentHelperBridge::CreateModel(
     const GURL& url) {
   DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);

components/arc/intent_helper/arc_intent_helper_bridge.h

@@ -56,6 +56,7 @@ class ArcIntentHelperBridge
 
   void AddObserver(ArcIntentHelperObserver* observer);
   void RemoveObserver(ArcIntentHelperObserver* observer);
+  bool HasObserver(ArcIntentHelperObserver* observer) const;
 
   // InstanceHolder<mojom::IntentHelperInstance>::Observer
   void OnInstanceReady() override;