Ignore duplicate FaviconHandler::OnUpdateFaviconURL() calls

components/favicon/core/favicon_handler.h

Index: components/favicon/core/favicon_handler.h
diff --git a/components/favicon/core/favicon_handler.h b/components/favicon/core/favicon_handler.h
index 4850f3c936d9d59cd7b8dd9d11aed289deec3e91..4449d3548ce846e4424e439a3417595ee5879a22 100644
--- a/components/favicon/core/favicon_handler.h
+++ b/components/favicon/core/favicon_handler.h
@@ -231,7 +231,9 @@ class FaviconHandler {
 
   // Return the current candidate if any.
   favicon::FaviconURL* current_candidate() {
-    return (!image_urls_.empty()) ? &image_urls_.front() : NULL;
+    return current_candidate_index_ < image_urls_.size()
+               ? &image_urls_[current_candidate_index_]
+               : nullptr;
   }
 
   // Returns the preferred size of the image. 0 means no preference (any size
@@ -242,10 +244,9 @@ class FaviconHandler {
     return handler_type_ == FAVICON ? gfx::kFaviconSize : 0;
   }
 
-  // Sorts the entries in |image_urls_| by icon size in descending order.
-  // Additionally removes any entries whose sizes are all greater than the max
-  // allowed size.
-  void SortAndPruneImageUrls();
+  // Sorts the entries in |image_urls| by icon size in descending order.
+  // Discards all but the largest size for each FaviconURL.
+  void SortAndPruneImageUrls(std::vector<FaviconURL>* image_urls);
 
   // Used for FaviconService requests.
   base::CancelableTaskTracker cancelable_task_tracker_;
@@ -288,6 +289,10 @@ class FaviconHandler {
   // This handler's driver, owns this object.
   FaviconDriver* driver_;
 
+  // The index of the favicon URL in |image_urls_| which is currently being
+  // requested from history or downloaded.
+  size_t current_candidate_index_;
+
   // Best image we've seen so far.  As images are downloaded from the page they
   // are stored here. When there is an exact match, or no more images are
   // available the favicon service and the current page are updated (assuming