[Large Icon Service] Move icon resizing into worker thread.

components/favicon/core/large_icon_service.h

Index: components/favicon/core/large_icon_service.h
diff --git a/components/favicon/core/large_icon_service.h b/components/favicon/core/large_icon_service.h
index bb8c1381f01ceaff4f7ece32adfbef69066f6056..042348acd8fe3199a84d6ea1e805749ad93f3792 100644
--- a/components/favicon/core/large_icon_service.h
+++ b/components/favicon/core/large_icon_service.h
@@ -7,12 +7,18 @@
 
 #include <vector>
 
+#include "base/memory/ref_counted.h"
 #include "base/task/cancelable_task_tracker.h"
+#include "base/threading/thread_checker.h"
 #include "components/favicon_base/favicon_callback.h"
 #include "components/keyed_service/core/keyed_service.h"
 
 class GURL;
 
+namespace base {
+class TaskRunner;
+}
+
 namespace favicon_base {
 struct FaviconRawBitmapResult;
 }
@@ -50,14 +56,25 @@ class LargeIconService : public KeyedService {
       const favicon_base::FaviconRawBitmapResult& bitmap_result,
       favicon_base::FaviconRawBitmapResult* resized_bitmap_result);
 
-  // Intermediate callback for GetLargeIconOrFallbackStyle(). Tries to resize
-  // |bitmap_result| and pass the output to |callback|. If that does not work,
-  // computes the icon fallback style and uses it to invoke |callback|.
+  // Tries to resize |bitmap_result| and pass the output to |callback|. If that
+  // does not work, computes the icon fallback style and uses it to invoke
+  // |callback|. The work is done on a background thread since image resizing
+  // can be expensive, and should not occur on the UI thread.
+  void RunLargeIconCallbackOnBackgroundThread(
+      const favicon_base::LargeIconCallback& callback,
+      int desired_size_in_pixel,
+      const favicon_base::FaviconRawBitmapResult& bitmap_result);
+
+  // Intermediate callback for GetLargeIconOrFallbackStyle().

[beaudoin, 2015/05/05 00:00:52]

// Meant to be invoked on the UI thread, this should not perform complex image
operations.

[huangs, 2015/05/05 15:22:13]

Done.

   void RunLargeIconCallback(
       const favicon_base::LargeIconCallback& callback,
       int desired_size_in_pixel,
+      base::CancelableTaskTracker* tracker,
       const favicon_base::FaviconRawBitmapResult& bitmap_result);
 
+  // Return the TaskRunner used to execute background task.
+  scoped_refptr<base::TaskRunner> GetBackgroundTaskRunner();
+
   FaviconService* favicon_service_;
 
   // A pre-populated list of the types of icon files to consider when looking
@@ -65,6 +82,8 @@ class LargeIconService : public KeyedService {
   // vector on each request.
   std::vector<int> large_icon_types_;
 
+  base::ThreadChecker thread_checker_;
+
   DISALLOW_COPY_AND_ASSIGN(LargeIconService);
 };