[Refactor] Simplify HistoryBackend::UpdateFaviconMappingsAndFetchImpl() signature

components/history/core/browser/history_service.h

Index: components/history/core/browser/history_service.h
diff --git a/components/history/core/browser/history_service.h b/components/history/core/browser/history_service.h
index c89868c9b4f974503c737d8b635469b089cd8f10..f240fedcb99b6597e107c453e1f5563df56087f7 100644
--- a/components/history/core/browser/history_service.h
+++ b/components/history/core/browser/history_service.h
@@ -644,18 +644,15 @@ class HistoryService : public syncer::SyncableService, public KeyedService {
   // FaviconService.
 
   // Used by FaviconService to get the favicon bitmaps from the history backend
-  // whose edge sizes most closely match |desired_sizes| for |icon_types|. If
+  // whose edge sizes most closely match |desired_sizes| for |icon_type|. If
   // |desired_sizes| has a '0' entry, the largest favicon bitmap for
-  // |icon_types| is returned. The returned FaviconBitmapResults will have at
+  // |icon_type| is returned. The returned FaviconBitmapResults will have at
   // most one result for each entry in |desired_sizes|. If a favicon bitmap is
   // determined to be the best candidate for multiple |desired_sizes| there will
   // be fewer results.
-  // If |icon_types| has several types, results for only a single type will be
-  // returned in the priority of TOUCH_PRECOMPOSED_ICON, TOUCH_ICON, and
-  // FAVICON.
-  base::CancelableTaskTracker::TaskId GetFavicons(
-      const std::vector<GURL>& icon_urls,
-      int icon_types,
+  base::CancelableTaskTracker::TaskId GetFavicon(
+      const GURL& icon_url,
+      favicon_base::IconType icon_type,
       const std::vector<int>& desired_sizes,
       const favicon_base::FaviconResultsCallback& callback,
       base::CancelableTaskTracker* tracker);
@@ -704,28 +701,16 @@ class HistoryService : public syncer::SyncableService, public KeyedService {
       const favicon_base::FaviconResultsCallback& callback,
       base::CancelableTaskTracker* tracker);
 
-  // Used by the FaviconService to replace the favicon mappings to |page_url|
-  // for |icon_types| on the history backend.
-  // Sample |icon_urls|:
-  //  { ICON_URL1 -> TOUCH_ICON, known to the database,
-  //    ICON_URL2 -> TOUCH_ICON, not known to the database,
-  //    ICON_URL3 -> TOUCH_PRECOMPOSED_ICON, known to the database }
-  // The new mappings are computed from |icon_urls| with these rules:
-  // 1) Any urls in |icon_urls| which are not already known to the database are
-  //    rejected.
-  //    Sample new mappings to |page_url|: { ICON_URL1, ICON_URL3 }
-  // 2) If |icon_types| has multiple types, the mappings are only set for the
-  //    largest icon type.
-  //    Sample new mappings to |page_url|: { ICON_URL3 }
-  // |icon_types| can only have multiple IconTypes if
-  // |icon_types| == TOUCH_ICON | TOUCH_PRECOMPOSED_ICON.
-  // The favicon bitmaps whose edge sizes most closely match |desired_sizes|
-  // from the favicons which were just mapped to |page_url| are returned. If
-  // |desired_sizes| has a '0' entry, the largest favicon bitmap is returned.
+  // Maps |page_url| to the favicon at |icon_url| if there is an entry in the
+  // database for |icon_url| and |icon_type|. This occurs when there is a
+  // mapping from a different page URL to |icon_url|. The favicon bitmaps whose
+  // edge sizes most closely match |desired_sizes| from the favicons which were
+  // just mapped to |page_url| are returned. If |desired_sizes| has a '0' entry,
+  // the largest favicon bitmap is returned.
   base::CancelableTaskTracker::TaskId UpdateFaviconMappingsAndFetch(
       const GURL& page_url,
-      const std::vector<GURL>& icon_urls,
-      int icon_types,
+      const GURL& icon_url,
+      favicon_base::IconType icon_type,
       const std::vector<int>& desired_sizes,
       const favicon_base::FaviconResultsCallback& callback,
       base::CancelableTaskTracker* tracker);