Don't request missing favicon on every page request.

chrome/browser/favicon/favicon_service.cc

Index: chrome/browser/favicon/favicon_service.cc
diff --git a/chrome/browser/favicon/favicon_service.cc b/chrome/browser/favicon/favicon_service.cc
index b762b19886e76adfb51da6044e1dc1c3cf85b05a..a60b63711c2901f55888c74177ae34b1b63e8e8a 100644
--- a/chrome/browser/favicon/favicon_service.cc
+++ b/chrome/browser/favicon/favicon_service.cc
@@ -4,6 +4,7 @@
 
 #include "chrome/browser/favicon/favicon_service.h"
 
+#include "base/hash.h"
 #include "base/message_loop_proxy.h"
 #include "chrome/browser/favicon/favicon_util.h"
 #include "chrome/browser/history/history_backend.h"
@@ -259,6 +260,20 @@ void FaviconService::SetFavicons(
   history_service_->SetFavicons(page_url, icon_type, favicon_bitmap_data);
 }
 
+void FaviconService::UnableToDownloadFavicon(const GURL& icon_url) {
+  MissingFaviconURLHash url_hash = base::Hash(icon_url.spec());

[palmer, 2013/05/13 17:22:47]

I don't think it matters a whole lot, but my instinct is to use a std::set.

[mef, 2013/05/14 18:47:08]

I thought about it, but hash_set seemed more natural fit as we don't care about
sorting order of missing url hashes.

+  missing_favicon_urls_.insert(url_hash);
+}
+
+bool FaviconService::WasUnableToDownloadFavicon(const GURL& icon_url) const {
+  MissingFaviconURLHash url_hash = base::Hash(icon_url.spec());
+  return missing_favicon_urls_.find(url_hash) != missing_favicon_urls_.end();
+}
+
+void FaviconService::ClearUnableToDownloadFavicons() {
+  missing_favicon_urls_.clear();
+}
+
 FaviconService::~FaviconService() {}
 
 CancelableTaskTracker::TaskId FaviconService::GetFaviconForURLImpl(
@@ -353,3 +368,4 @@ void FaviconService::RunFaviconRawCallbackWithBitmapResults(
       &resized_bitmap_data);
   callback.Run(bitmap_result);
 }
+