[AiS] Add prefetching for Answers images.

chrome/browser/bitmap_fetcher/bitmap_fetcher_service.cc

 // Copyright 2014 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/bitmap_fetcher/bitmap_fetcher_service.h"
 
 #include "base/memory/weak_ptr.h"
 #include "chrome/browser/bitmap_fetcher/bitmap_fetcher.h"
 #include "chrome/browser/profiles/profile.h"
 #include "net/base/load_flags.h"
@@ skipping 97 matching lines @@
   const chrome::BitmapFetcher* fetcher = FindFetcherForUrl(url);
   if (fetcher)
     return fetcher;
 
   chrome::BitmapFetcher* new_fetcher = CreateFetcher(url);
   active_fetchers_.push_back(new_fetcher);
   return new_fetcher;
 }
 
 void BitmapFetcherService::Prefetch(const GURL& url) {
+  if (!url.is_valid())
+    return;
   (void)EnsureFetcherForUrl(url);

[Peter Kasting, 2014/06/14 01:00:51]

Nit: While here, please fix this; we disallow C-style casts.  If removing this
causes some sort of warning that we're ignoring the result of something marked
with WARN_UNUSED_RESULT, use the ignore_result() method from base/macros.h.

[groby-ooo-7-16, 2014/06/17 21:06:35]

Fixed in base-cl. Also, inverted logic to kill early-out return.

 }
 
 RequestId BitmapFetcherService::RequestImage(const GURL& url,
                                             BitmapFetcherObserver* observer) {
   // Create a new request, assigning next available request ID.
   ++current_request_id_;
   if (current_request_id_ == REQUEST_ID_INVALID)
     ++current_request_id_;
   int request_id = current_request_id_;
   scoped_ptr<BitmapFetcherRequest> request(
@@ skipping 41 matching lines @@
   }
 
   if (!bitmap->isNull()) {
     CacheEntry* entry = new CacheEntry;
     entry->bitmap.reset(new SkBitmap(*bitmap));
     cache_.Put(fetcher->url(), entry);
   }
 
   RemoveFetcher(fetcher);
 }