Avoid retaining a reference to ActivityIconLoader in its OnIconReady()

components/arc/intent_helper/activity_icon_loader.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 "components/arc/intent_helper/activity_icon_loader.h"
 
 #include <string.h>
 
 #include <tuple>
 #include <utility>
@@ skipping 145 matching lines @@
   return true;
 }
 
 void ActivityIconLoader::OnIconsReady(
     std::unique_ptr<ActivityToIconsMap> cached_result,
     const OnIconsReadyCallback& cb,
     std::vector<mojom::ActivityIconPtr> icons) {
   ArcServiceManager* manager = ArcServiceManager::Get();
   base::PostTaskAndReplyWithResult(
       manager->blocking_task_runner().get(), FROM_HERE,
-      base::Bind(&ActivityIconLoader::ResizeAndEncodeIcons, this,
-                 base::Passed(&icons)),
+      base::Bind(&ActivityIconLoader::ResizeAndEncodeIcons,

[hidehiko, 2017/01/26 13:14:20]

(I know it is not your mistake, but ...)

ResizeAndEncodeIcons can be static. So could you mark as static and remove
"this" from here, instead?

thread_checker_ DCHECK looks wrong check, because this instance is created on
the browser thread, while the method should run on a BlockingPool thread, so
could you remove it?

You can keep the field, because we still want to check the thread where other
methods run. So, as you're here, could you add

DCHECK(thread_checker_.CalledOnValidThread()); 

to the beginning of the following methods?
- InvalidateIcons()
- GetActivityIcons()
- OnIconsReady() and
- OnIconsResized().

[tzik, 2017/01/26 13:21:12]

Done.

+                 base::Unretained(this), base::Passed(&icons)),
       base::Bind(&ActivityIconLoader::OnIconsResized, this,
                  base::Passed(&cached_result), cb));
 }
 
 std::unique_ptr<ActivityIconLoader::ActivityToIconsMap>
 ActivityIconLoader::ResizeAndEncodeIcons(
     std::vector<mojom::ActivityIconPtr> icons) {
   // Runs only on the blocking pool.
   DCHECK(thread_checker_.CalledOnValidThread());
   std::unique_ptr<ActivityToIconsMap> result(new ActivityToIconsMap);
@@ skipping 56 matching lines @@
     cached_icons_.erase(kv.first);
     cached_icons_.insert(std::make_pair(kv.first, kv.second));
   }
 
   // Merge the results that were obtained from cache before doing IPC.
   result->insert(cached_result->begin(), cached_result->end());
   cb.Run(std::move(result));
 }
 
 }  // namespace arc