favicon: makes FaviconHandler::FetchFavicon() early out

Specifically if the url is the same as the last page and the
navigation is a same-document navigation, then FaviconHandler need
not do anything. This scenario happens when using
history.replaceState() and the like (which is used on the SRP).

BUG=none
TEST=covered by test

Change-Id: Ida3aabeefb1cef033b68b667049fa724efe7b4f8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2335024Reviewed-by: Peter Kotwicz <pkotwicz@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#794559}

components/favicon/core/favicon_handler.cc

@@ -190,6 +190,12 @@ favicon_base::IconTypeSet FaviconHandler::GetIconTypesFromHandlerType(
 }
 
 void FaviconHandler::FetchFavicon(const GURL& page_url, bool is_same_document) {
+  // Some same document navigations (such as those done by
+  // history.replaceState) do not change the url. No need to start over in this
+  // case.
+  if (is_same_document && page_url == last_page_url_)
+    return;
+
   cancelable_task_tracker_for_page_url_.TryCancelAll();
   cancelable_task_tracker_for_candidates_.TryCancelAll();
 

components/favicon/core/favicon_handler_unittest.cc

@@ -579,6 +579,18 @@ TEST_F(FaviconHandlerTest, UpdateFaviconMappingsAndFetch) {
   RunHandlerWithSimpleFaviconCandidates({kIconURL16x16});
 }
 
+// Verifies same document navigation to the last page does not trigger fetch.
+TEST_F(FaviconHandlerTest, SameDocumentNavigationToLastUrlDoesNotFetchAgain) {
+  EXPECT_CALL(favicon_service_,
+              UpdateFaviconMappingsAndFetch(base::flat_set<GURL>{kPageURL},
+                                            kIconURL16x16, kFavicon,
+                                            /*desired_size_in_dip=*/16, _, _));
+  EXPECT_CALL(favicon_service_, GetFaviconForPageURL(_, _, _, _, _)).Times(1);
+
+  auto handler = RunHandlerWithSimpleFaviconCandidates({kIconURL16x16});
+  handler->FetchFavicon(kPageURL, true);
+}
+
 // Test that we don't try to delete favicon mappings when a page URL is not in
 // history even if the page lists no favicons.
 TEST_F(FaviconHandlerTest, DoNotDeleteFaviconMappingsIfNotInHistory) {