Migrate AddToHomescreenDataFetcher to use TaskScheduler.

chrome/browser/android/webapps/add_to_homescreen_data_fetcher.h

Index: chrome/browser/android/webapps/add_to_homescreen_data_fetcher.h
diff --git a/chrome/browser/android/webapps/add_to_homescreen_data_fetcher.h b/chrome/browser/android/webapps/add_to_homescreen_data_fetcher.h
index 4dc6b26cde9e37477445bb083987632044c31056..77679690d61eab35b03463ad41c6607702cc9e87 100644
--- a/chrome/browser/android/webapps/add_to_homescreen_data_fetcher.h
+++ b/chrome/browser/android/webapps/add_to_homescreen_data_fetcher.h
@@ -7,28 +7,17 @@
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
+#include "base/strings/string16.h"
 #include "base/task/cancelable_task_tracker.h"
 #include "base/timer/timer.h"
 #include "chrome/browser/android/shortcut_info.h"
 #include "content/public/browser/web_contents_observer.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 
-namespace base {
-class TaskRunner;
-}
-
-namespace content {
-class WebContents;
-}
-
 namespace favicon_base {
 struct FaviconRawBitmapResult;
 }
 
-namespace IPC {
-class Message;
-}
-
 class GURL;
 struct InstallableData;
 struct WebApplicationInfo;
@@ -123,8 +112,6 @@ class AddToHomescreenDataFetcher
   // Notifies the observer that the shortcut data is all available.
   void NotifyObserver(const SkBitmap& icon);
 
-  scoped_refptr<base::TaskRunner> background_task_runner_;
-
   Observer* weak_observer_;
 
   // The icons must only be set on the UI thread for thread safety.