Revert of ios: Remove use of MessageLoopProxy and deprecated MessageLoop APIs

ios/chrome/browser/snapshots/snapshot_cache.mm

 // Copyright 2012 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.
 
 #import "ios/chrome/browser/snapshots/snapshot_cache.h"
 
 #import <UIKit/UIKit.h>
 
 #include "base/critical_closure.h"
 #include "base/files/file_enumerator.h"
@@ skipping 194 matching lines @@
     return;
 
   UIImage* img = [imageDictionary_ objectForKey:sessionID];
   if (img) {
     if (callback)
       callback(img);
     return;
   }
 
   base::PostTaskAndReplyWithResult(
-      web::WebThread::GetTaskRunnerForThread(web::WebThread::FILE_USER_BLOCKING)
-          .get(),
+      web::WebThread::GetMessageLoopProxyForThread(
+          web::WebThread::FILE_USER_BLOCKING).get(),
       FROM_HERE, base::BindBlock(^base::scoped_nsobject<UIImage>() {
         // Retrieve the image on a high priority thread.
         return base::scoped_nsobject<UIImage>([ReadImageFromDisk(
             [SnapshotCache imagePathForSessionID:sessionID]) retain]);
       }),
       base::BindBlock(^(base::scoped_nsobject<UIImage> image) {
         // The iPad tab switcher is currently using its own memory cache so the
         // image is not stored in memory here if running on iPad.
         // The same logic is used on image writes (code below).
         if (!IsIPadIdiom() && image)
@@ skipping 167 matching lines @@
   }
 }
 
 - (void)loadGreyImageAsync:(NSString*)sessionID {
   DCHECK_CURRENTLY_ON_WEB_THREAD(web::WebThread::UI);
   // Don't call -retrieveImageForSessionID here because it caches the colored
   // image, which we don't need for the grey image cache. But if the image is
   // already in the cache, use it.
   UIImage* img = [imageDictionary_ objectForKey:sessionID];
   base::PostTaskAndReplyWithResult(
-      web::WebThread::GetTaskRunnerForThread(web::WebThread::FILE_USER_BLOCKING)
-          .get(),
-      FROM_HERE, base::BindBlock(^base::scoped_nsobject<UIImage>() {
+      web::WebThread::GetMessageLoopProxyForThread(
+          web::WebThread::FILE_USER_BLOCKING).get(),
+      FROM_HERE,
+      base::BindBlock(^base::scoped_nsobject<UIImage>() {
         base::scoped_nsobject<UIImage> result([img retain]);
         // If the image is not in the cache, load it from disk.
         if (!result)
           result.reset([ReadImageFromDisk(
               [SnapshotCache imagePathForSessionID:sessionID]) retain]);
         if (result)
           result.reset([GreyImage(result) retain]);
         return result;
       }),
       base::BindBlock(^(base::scoped_nsobject<UIImage> greyImage) {
@@ skipping 40 matching lines @@
   DCHECK_CURRENTLY_ON_WEB_THREAD(web::WebThread::UI);
   if (greyImageDictionary_) {
     UIImage* image = [greyImageDictionary_ objectForKey:sessionID];
     if (image) {
       callback(image);
       return;
     }
   }
 
   base::PostTaskAndReplyWithResult(
-      web::WebThread::GetTaskRunnerForThread(web::WebThread::FILE_USER_BLOCKING)
-          .get(),
-      FROM_HERE, base::BindBlock(^base::scoped_nsobject<UIImage>() {
+      web::WebThread::GetMessageLoopProxyForThread(
+          web::WebThread::FILE_USER_BLOCKING).get(),
+      FROM_HERE,
+      base::BindBlock(^base::scoped_nsobject<UIImage>() {
         // Retrieve the image on a high priority thread.
         // Loading the file into NSData is more reliable.
         // -imageWithContentsOfFile would ocassionally claim the image was not a
         // valid jpg.
         // "ImageIO: <ERROR> JPEGNot a JPEG file: starts with 0xff 0xd9"
         // See
         // http://stackoverflow.com/questions/5081297/ios-uiimagejpegrepresentation-error-not-a-jpeg-file-starts-with-0xff-0xd9
         NSData* imageData = [NSData
             dataWithContentsOfFile:base::SysUTF8ToNSString(
                 [SnapshotCache greyImagePathForSessionID:sessionID].value())];
@@ skipping 33 matching lines @@
       backgroundingImageSessionId_.reset();
     }
   }
 
   web::WebThread::PostBlockingPoolTask(
       FROM_HERE, base::Bind(&ConvertAndSaveGreyImage, colorImagePath,
                             greyImagePath, backgroundingColorImage_));
 }
 
 @end