Calls ShortcutHelper::FinalizeLauncherIcon() on worker thread instead of on IO thread

chrome/browser/android/webapps/add_to_homescreen_data_fetcher.cc

 // Copyright 2015 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 "chrome/browser/android/webapps/add_to_homescreen_data_fetcher.h"
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/location.h"
 #include "base/strings/string16.h"
@@ skipping 193 matching lines @@
       threshold_to_get_any_largest_icon,
       base::Bind(&AddToHomescreenDataFetcher::OnFaviconFetched, this),
       &favicon_task_tracker_);
 }
 
 void AddToHomescreenDataFetcher::OnFaviconFetched(
     const favicon_base::FaviconRawBitmapResult& bitmap_result) {
   if (!web_contents() || !weak_observer_ || is_icon_saved_)
     return;
 
-  content::BrowserThread::PostTask(
-      content::BrowserThread::IO,
+  content::BrowserThread::PostBlockingPoolTask(
       FROM_HERE,
-      base::Bind(&AddToHomescreenDataFetcher::CreateLauncherIcon,
-                 this,
-                 bitmap_result));
+      base::Bind(&AddToHomescreenDataFetcher::CreateLauncherIconInBackground,
+                 this, bitmap_result));
 }
 
-void AddToHomescreenDataFetcher::CreateLauncherIcon(
+void AddToHomescreenDataFetcher::CreateLauncherIconInBackground(
     const favicon_base::FaviconRawBitmapResult& bitmap_result) {
   if (!web_contents() || !weak_observer_) return;

[Yaron, 2016/08/09 20:52:19]

Hmm. I don't think we should check the web_contents() here and the background
thread logic doesn't actually depend on it. Instead, it should be checked when
passed back to the UI thread.

 
-  DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
+  DCHECK(content::BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());
   SkBitmap icon_bitmap;
   if (bitmap_result.is_valid()) {
     gfx::PNGCodec::Decode(bitmap_result.bitmap_data->front(),
                           bitmap_result.bitmap_data->size(),
                           &icon_bitmap);
   }
 
   bool is_generated = false;
   if (weak_observer_) {
-    icon_bitmap = weak_observer_->FinalizeLauncherIcon(icon_bitmap,
-                                                       shortcut_info_.url,
-                                                       &is_generated);
+    icon_bitmap = weak_observer_->FinalizeLauncherIconInBackground(
+        icon_bitmap, shortcut_info_.url, &is_generated);

[Yaron, 2016/08/09 20:52:18]

similarly, the url should be passed in, mutated (currently on L238) and then
passed back as part of the ::NotifyObserver call.

   }
 
   shortcut_info_.icon_url = is_generated ? GURL() : bitmap_result.icon_url;
   content::BrowserThread::PostTask(
       content::BrowserThread::UI, FROM_HERE,
       base::Bind(&AddToHomescreenDataFetcher::NotifyObserver, this,
                  icon_bitmap));
 }
 
 void AddToHomescreenDataFetcher::OnManifestIconFetched(const GURL& icon_url,
@@ skipping 23 matching lines @@
 
   // If URL points to an offline content, get original URL.
   GURL online_url =
       offline_pages::OfflinePageUtils::MaybeGetOnlineURLForOfflineURL(
           web_contents()->GetBrowserContext(), original_url);
   if (online_url.is_valid())
     return online_url;
 
   return original_url;
 }