Add possibility to define data callback to BitmapFetcher

chrome/browser/bitmap_fetcher/bitmap_fetcher.h

Index: chrome/browser/bitmap_fetcher/bitmap_fetcher.h
diff --git a/chrome/browser/bitmap_fetcher/bitmap_fetcher.h b/chrome/browser/bitmap_fetcher/bitmap_fetcher.h
index 11055eaf61a50e8aaf7a051e629858c5435e7de5..d498695c4fba6ba25c15dd9aceae8f605ff341e4 100644
--- a/chrome/browser/bitmap_fetcher/bitmap_fetcher.h
+++ b/chrome/browser/bitmap_fetcher/bitmap_fetcher.h
@@ -29,17 +29,23 @@ class BitmapFetcher : public net::URLFetcherDelegate,
   ~BitmapFetcher() override;
 
   const GURL& url() const { return url_; }
+  net::URLFetcher* url_fetcher() { return url_fetcher_.get(); }
+
+  // Initializes internal fetcher.  After this function returns url_fetcher()
+  // can be accessed to configure it further(eg. add user data to request).

[Theresa, 2015/05/04 16:57:39]

nit, missing space: "further (e.g. add...)"

+  // All configuration must be done before Start() is called.
+  // Values for |load_flags| are defined in net/base/load_flags.h.  In general,
+  // |net::LOAD_NORMAL| is appropriate.
+  void Init(net::URLRequestContextGetter* request_context,
+            const std::string& referrer,

[dschuyler, 2015/05/05 20:45:50]

No big deal, but I noticed that each of the calls seem to pass a blank string
here.  Maybe consider removing this parameter from Init and have callers use the
url_fether() to set the referrer if desired.  Maybe in another CL though - I
don't think this should hold up this CL.

+            net::URLRequest::ReferrerPolicy referrer_policy,
+            int load_flags);
 
   // Start fetching the URL with the fetcher. The delegate is notified
   // asynchronously when done.  Start may be called more than once in some
   // cases.  If so, subsequent starts will be ignored since the operation is
-  // already in progress.  Arguments are used to configure the internal fetcher.
-  // Values for |load_flags| are defined in net/base/load_flags.h.  In general,
-  // |net::LOAD_NORMAL| is appropriate.
-  void Start(net::URLRequestContextGetter* request_context,
-             const std::string& referrer,
-             net::URLRequest::ReferrerPolicy referrer_policy,
-             int load_flags);
+  // already in progress.
+  void Start();
 
   // Methods inherited from URLFetcherDelegate