Media Galleries: Migrate MediaGalleriesPreferences to TaskScheduler

Bug: 689520
Change-Id: Ie683b101ea28f68aa0e96696cccf5345a60bb1ea
Reviewed-on: https://chromium-review.googlesource.com/578440
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tommy Li <tommycli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#489126}

chrome/browser/media_galleries/media_galleries_preferences.cc

@@ -19,6 +19,9 @@
 #include "base/strings/string16.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/task_scheduler/post_task.h"
+#include "base/task_scheduler/task_traits.h"
+#include "base/threading/thread_restrictions.h"
 #include "base/values.h"
 #include "build/build_config.h"
 #include "chrome/browser/browser_process.h"
@@ -363,8 +366,8 @@ base::string16 GetDisplayNameForSubFolder(const base::string16& device_name,
           device_name);
 }
 
-void InitializeImportedMediaGalleryRegistryOnFileThread() {
-  DCHECK_CURRENTLY_ON(content::BrowserThread::FILE);
+void InitializeImportedMediaGalleryRegistryInBackground() {
+  base::ThreadRestrictions::AssertIOAllowed();
   ImportedMediaGalleryRegistry::GetInstance()->Initialize();
 }
 
@@ -522,13 +525,15 @@ bool MediaGalleriesPreferences::IsInitialized() const { return initialized_; }
 Profile* MediaGalleriesPreferences::profile() { return profile_; }
 
 void MediaGalleriesPreferences::OnInitializationCallbackReturned() {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   DCHECK(!IsInitialized());
   DCHECK_GT(pre_initialization_callbacks_waiting_, 0);
   if (--pre_initialization_callbacks_waiting_ == 0)
     FinishInitialization();
 }
 
 void MediaGalleriesPreferences::FinishInitialization() {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   DCHECK(!IsInitialized());
 
   initialized_ = true;
@@ -669,9 +674,9 @@ void MediaGalleriesPreferences::OnFinderDeviceID(const std::string& device_id) {
 
     if (!gallery_name.empty()) {
       pre_initialization_callbacks_waiting_++;
-      content::BrowserThread::PostTaskAndReply(
-          content::BrowserThread::FILE, FROM_HERE,
-          base::BindOnce(&InitializeImportedMediaGalleryRegistryOnFileThread),
+      base::PostTaskWithTraitsAndReply(
+          FROM_HERE, {base::MayBlock(), base::TaskPriority::BACKGROUND},
+          base::BindOnce(&InitializeImportedMediaGalleryRegistryInBackground),
           base::BindOnce(
               &MediaGalleriesPreferences::OnInitializationCallbackReturned,
               weak_factory_.GetWeakPtr()));

chrome/browser/media_galleries/media_galleries_preferences.h

@@ -186,7 +186,7 @@ class MediaGalleriesPreferences
   // Before the callback is run, other calls may not return the correct results.
   // Should be invoked on the UI thread; callbacks will be run on the UI thread.
   // This call also ensures that the StorageMonitor is initialized.
-  // Note for unit tests: This requires an active FILE thread and
+  // Note for unit tests: This requires an active ScopedTaskEnvironment and
   // EnsureMediaDirectoriesExists instance to complete reliably.
   void EnsureInitialized(base::Closure callback);
 

chrome/browser/media_galleries/media_galleries_preferences_unittest.cc

@@ -18,6 +18,7 @@
 #include "base/path_service.h"
 #include "base/run_loop.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/values.h"
 #include "build/build_config.h"
 #include "chrome/browser/extensions/test_extension_system.h"
@@ -111,9 +112,10 @@ class MediaGalleriesPreferencesTest : public testing::Test {
       DeviceIdPrefIdsMap;
 
   MediaGalleriesPreferencesTest()
-      : profile_(new TestingProfile()),
-        default_galleries_count_(0) {
-  }
+      : scoped_task_environment_(
+            base::test::ScopedTaskEnvironment::MainThreadType::UI),
+        profile_(new TestingProfile()),
+        default_galleries_count_(0) {}
 
   ~MediaGalleriesPreferencesTest() override {}
 
@@ -364,6 +366,8 @@ class MediaGalleriesPreferencesTest : public testing::Test {
   MediaGalleriesPrefInfoMap expected_galleries_;
 
  private:
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
+
   // Needed for extension service & friends to work.
   content::TestBrowserThreadBundle thread_bundle_;