Avoid sending notifications when the bitmap data in history has not changed

chrome/browser/history/history_backend.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/history/history_backend.h"
 
 #include <algorithm>
 #include <functional>
 #include <list>
 #include <map>
@@ skipping 1913 matching lines @@
   }
 
   std::vector<FaviconBitmapIDSize> bitmap_id_sizes;
   thumbnail_db_->GetFaviconBitmapIDSizes(favicon_id, &bitmap_id_sizes);
 
   // If there is already a favicon bitmap of |pixel_size| at |icon_url|,
   // replace it.
   bool replaced_bitmap = false;
   for (size_t i = 0; i < bitmap_id_sizes.size(); ++i) {
     if (bitmap_id_sizes[i].pixel_size == pixel_size) {
+      if (IsFaviconBitmapDataEqual(bitmap_id_sizes[i].bitmap_id, bitmap_data)) {
+        thumbnail_db_->SetFaviconBitmapLastUpdateTime(
+            bitmap_id_sizes[i].bitmap_id, base::Time::Now());
+        // Return early as merging did not alter the bitmap data.
+        ScheduleCommit();
+        return;
+      }
       thumbnail_db_->SetFaviconBitmap(bitmap_id_sizes[i].bitmap_id, bitmap_data,
           base::Time::Now());
       replaced_bitmap = true;
       break;
     }
   }
 
   // Create a vector of the pixel sizes of the favicon bitmaps currently at
   // |icon_url|.
   std::vector<gfx::Size> favicon_sizes;
@@ skipping 365 matching lines @@
     const gfx::Size& pixel_size = bitmap_id_sizes[i].pixel_size;
     FaviconSizes::const_iterator sizes_it = std::find(favicon_sizes.begin(),
         favicon_sizes.end(), pixel_size);
     if (sizes_it == favicon_sizes.end())
       thumbnail_db_->DeleteFaviconBitmap(bitmap_id_sizes[i].bitmap_id);
   }
 
   thumbnail_db_->SetFaviconSizes(icon_id, favicon_sizes);
 }
 
+bool HistoryBackend::IsFaviconBitmapDataEqual(
+    FaviconBitmapID bitmap_id,
+    const scoped_refptr<base::RefCountedMemory>& new_bitmap_data) {
+  if (!new_bitmap_data.get())
+    return false;
+
+  scoped_refptr<base::RefCountedMemory> original_bitmap_data;
+  thumbnail_db_->GetFaviconBitmap(bitmap_id,
+                                  NULL,
+                                  &original_bitmap_data,
+                                  NULL);
+  return new_bitmap_data->Equals(original_bitmap_data);
+}
+
 bool HistoryBackend::GetFaviconsFromDB(
     const GURL& page_url,
     int icon_types,
     int desired_size_in_dip,
     const std::vector<ui::ScaleFactor>& desired_scale_factors,
     std::vector<FaviconBitmapResult>* favicon_bitmap_results,
     IconURLSizesMap* icon_url_sizes) {
   DCHECK(favicon_bitmap_results);
   DCHECK(icon_url_sizes);
   favicon_bitmap_results->clear();
@@ skipping 648 matching lines @@
   info.url_id = visit.url_id;
   info.time = visit.visit_time;
   info.transition = visit.transition;
   // If we don't have a delegate yet during setup or shutdown, we will drop
   // these notifications.
   if (delegate_.get())
     delegate_->NotifyVisitDBObserversOnAddVisit(info);
 }
 
 }  // namespace history