Fixes flickering in chrome://settings/startup with the scheduler enabled

Previously CustomHomePagesTableModel::SetToCurrentlyOpenPages was
sending a large number of StartupOverlay.updateStartupPages with
intermediate state as pre-existing rows where removed and then new ones
added and their titles looked up.  This became a problem with the blink
scheduler enabled on touch devices, because a touch puts the renderer
scheduler into compositor priority and generated more frames than before
leading to horrible flickering of the dialog.

This patch fixes that by only sending a single update once all of the
titles have been looked up.

BUG=450953

Review URL: https://codereview.chromium.org/870563003

Cr-Commit-Position: refs/heads/master@{#312695}

1 files changed, 25 insertions, 1 deletions

diff --git a/chrome/browser/custom_home_pages_table_model.h b/chrome/browser/custom_home_pages_table_model.h
index ca19997..797cc14 100644
--- a/chrome/browser/custom_home_pages_table_model.h
+++ b/chrome/browser/custom_home_pages_table_model.h
@@ -68,13 +68,33 @@ class CustomHomePagesTableModel : public ui::TableModel {
   // Loads the title for the specified entry.
   void LoadTitle(Entry* entry);
 
+  // Loads all the titles, notifies the observer of the change once all loads
+  // are complete.
+  void LoadAllTitles();
+
   // Callback from history service. Updates the title of the Entry whose
-  // |url| matches |entry_url| and notifies the observer of the change.
+  // |url| matches |entry_url| and notifies the observer of the change if
+  // |observable| is true.
   void OnGotTitle(const GURL& entry_url,
+                  bool observable,
                   bool found_url,
                   const history::URLRow& row,
                   const history::VisitVector& visits);
 
+  // Like OnGotTitle, except that num_outstanding_title_lookups_ is decremented
+  // and if the count reaches zero the observer is notifed.
+  void OnGotOneOfManyTitles(const GURL& entry_url,
+                            bool found_url,
+                            const history::URLRow& row,
+                            const history::VisitVector& visits);
+
+  // Adds an entry at the specified index, but doesn't load the title or tell
+  // the observer.
+  void AddWithoutNotification(int index, const GURL& url);
+
+  // Removes the entry at the specified index, but doesn't tell the observer.
+  void RemoveWithoutNotification(int index);
+
   // Returns the URL for a particular row, formatted for display to the user.
   base::string16 FormattedURL(int row) const;
 
@@ -89,6 +109,10 @@ class CustomHomePagesTableModel : public ui::TableModel {
   // Used in loading titles.
   base::CancelableTaskTracker task_tracker_;
 
+  // Used to keep track of when it's time to update the observer when loading
+  // multiple titles.
+  int num_outstanding_title_lookups_;
+
   DISALLOW_COPY_AND_ASSIGN(CustomHomePagesTableModel);
 };