[AiS] Add prefetching for Answers images.

chrome/browser/bitmap_fetcher/bitmap_fetcher_service.cc

Index: chrome/browser/bitmap_fetcher/bitmap_fetcher_service.cc
diff --git a/chrome/browser/bitmap_fetcher/bitmap_fetcher_service.cc b/chrome/browser/bitmap_fetcher/bitmap_fetcher_service.cc
index 7e332d811901933f9e6a8f4cc943d60eba34a827..ae705bed9d3a8ac10b71fd0487bb55eaf5a0d5fb 100644
--- a/chrome/browser/bitmap_fetcher/bitmap_fetcher_service.cc
+++ b/chrome/browser/bitmap_fetcher/bitmap_fetcher_service.cc
@@ -115,6 +115,8 @@ const chrome::BitmapFetcher* BitmapFetcherService::EnsureFetcherForUrl(
 }
 
 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.

 }