Don't request missing favicon on every page request.

chrome/browser/favicon/favicon_service.h

Index: chrome/browser/favicon/favicon_service.h
diff --git a/chrome/browser/favicon/favicon_service.h b/chrome/browser/favicon/favicon_service.h
index 12ad68834af2e8c2b0c41d159564fd19ade4bf12..f3a2dbe992d70e0fb8bf7d2e2b30eb1edaab1391 100644
--- a/chrome/browser/favicon/favicon_service.h
+++ b/chrome/browser/favicon/favicon_service.h
@@ -8,6 +8,7 @@
 #include <vector>
 
 #include "base/callback.h"
+#include "base/hash_tables.h"
 #include "base/memory/ref_counted.h"
 #include "chrome/browser/common/cancelable_request.h"
 #include "chrome/browser/history/history_types.h"
@@ -223,7 +224,12 @@ class FaviconService : public CancelableRequestProvider,
       history::IconType icon_type,
       const gfx::Image& image);
 
+  // Avoid repeated requests to download missing favicon (crbug 39402).

[pauljensen, 2013/04/30 14:38:04]

The prevailing style is crbug.com/39402.

[mef, 2013/04/30 21:57:03]

Done.

+  void AddMissingFavicon(const GURL& icon_url);
+  bool IsMissingFavicon(const GURL& icon_url) const;
+
  private:
+  base::hash_set<int32>  missing_favicon_urls_;

[mef, 2013/04/29 21:55:03]

Lint suggests to add #include for hash_set<>, which appears to be hash_tables.h,
yet it is still unhappy.

[pauljensen, 2013/04/30 14:38:04]

Ya, I think lint is wrong and your code is correct.  I've run into this before.

[pauljensen, 2013/04/30 14:38:04]

You should not use int32.  The Google C++ coding style recommends the C99 types
like int32_t, though I see base::Hash returns an uint32.  The Chromium coding
style says to use unsigned types for hash values.  I would recommend typedef'ing
this because you use it in two different files.  Maybe:
  typedef uint32 MissingFaviconURLHashValue;
or maybe with a shorter name.

[mef, 2013/04/30 21:57:03]

Done.

[mef, 2013/04/30 21:57:03]

Done.

   HistoryService* history_service_;
 
   // Helper function for GetFaviconImageForURL(), GetRawFaviconForURL() and