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

chrome/browser/history/history_backend.h

Index: chrome/browser/history/history_backend.h
diff --git a/chrome/browser/history/history_backend.h b/chrome/browser/history/history_backend.h
index ab0acb867eb890c3bdba179b6b2e155c17aaa6f0..7531a9ab1fb311ff033006f81d23e1a51a5c3c80 100644
--- a/chrome/browser/history/history_backend.h
+++ b/chrome/browser/history/history_backend.h
@@ -676,9 +676,12 @@ class HistoryBackend : public base::RefCountedThreadSafe<HistoryBackend>,
   // For each entry in |favicon_bitmap_data|, if a favicon bitmap already
   // exists at the entry's pixel size, replace the favicon bitmap's data with
   // the entry's bitmap data. Otherwise add a new favicon bitmap.
+  // If not NULL, |favicon_bitmaps_changed| is set to whether any of the bitmap
+  // data at |icon_id| is changed as a result of calling this method.
   void SetFaviconBitmaps(
       FaviconID icon_id,
-      const std::vector<FaviconBitmapData>& favicon_bitmap_data);
+      const std::vector<FaviconBitmapData>& favicon_bitmap_data,
+      bool* favicon_bitmaps_changed);
 
   // Returns true if |favicon_bitmap_data| and |icon_url_sizes| passed to
   // SetFavicons() are valid.
@@ -700,8 +703,16 @@ class HistoryBackend : public base::RefCountedThreadSafe<HistoryBackend>,
   // detailed description of FaviconSizes.
   // Deletes any favicon bitmaps currently mapped to |icon_id| whose pixel
   // sizes are not contained in |favicon_sizes|.
+  // |favicon_bitmaps_deleted| is set to true if at least one favicon bitmap
+  // is deleted.
   void SetFaviconSizes(FaviconID icon_id,
-                       const FaviconSizes& favicon_sizes);
+                       const FaviconSizes& favicon_sizes,
+                       bool* favicon_bitmaps_deleted);
+
+  // Returns true if |new_bitmap_data| equals the bitmap data at |bitmap_id|.
+  bool IsFaviconBitmapDataEqual(
+      FaviconBitmapID bitmap_id,
+      const scoped_refptr<base::RefCountedMemory>& new_bitmap_data);
 
   // Returns true if there are favicons for |page_url| and one of the types in
   // |icon_types|.