Don't request missing favicon on every page request.

chrome/browser/favicon/favicon_service.cc

 // Copyright (c) 2012 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/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"
 #include "chrome/browser/history/history_service.h"
 #include "chrome/browser/history/history_service_factory.h"
 #include "chrome/browser/history/select_favicon_frames.h"
 #include "chrome/browser/ui/webui/chrome_web_ui_controller_factory.h"
 #include "chrome/common/url_constants.h"
 #include "extensions/common/constants.h"
 #include "third_party/skia/include/core/SkBitmap.h"
@@ skipping 235 matching lines @@
       bitmap_data_element.pixel_size = pixel_size;
       bitmap_data_element.icon_url = icon_url;
 
       favicon_bitmap_data.push_back(bitmap_data_element);
     }
   }
 
   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(
     const FaviconForURLParams& params,
     const std::vector<ui::ScaleFactor>& desired_scale_factors,
     const FaviconResultsCallback& callback,
     CancelableTaskTracker* tracker) {
   if (params.page_url.SchemeIs(chrome::kChromeUIScheme) ||
       params.page_url.SchemeIs(extensions::kExtensionScheme)) {
     CancelableTaskTracker::IsCanceledCallback is_canceled_cb;
@@ skipping 74 matching lines @@
   if (!gfx::PNGCodec::EncodeBGRASkBitmap(resized_image.AsBitmap(), false,
                                          &resized_bitmap_data)) {
     callback.Run(history::FaviconBitmapResult());
     return;
   }
 
   bitmap_result.bitmap_data = base::RefCountedBytes::TakeVector(
       &resized_bitmap_data);
   callback.Run(bitmap_result);
 }
+