[Mac] Fix for fullscreen tabstrip animation

Fix for an issue where the tabstrip animates out when you're still
cycling between tabs.

BUG=591776

Review-Url: https://codereview.chromium.org/2672913002
Cr-Commit-Position: refs/heads/master@{#448014}

chrome/browser/ui/cocoa/fullscreen/fullscreen_toolbar_animation_controller.mm

@@ -54,17 +54,19 @@ void FullscreenToolbarAnimationController::AnimateToolbarForTabstripChanges() {
   if ([owner_ mustShowFullscreenToolbar])
     return;
 
-  AnimateToolbarIn();
+  if (animation_.IsShowing()) {
+    hide_toolbar_timer_.Reset();
+    return;
+  }
+
   should_hide_toolbar_after_delay_ = true;
+  AnimateToolbarIn();
 }
 
 void FullscreenToolbarAnimationController::AnimateToolbarIn() {
   if (![owner_ isInFullscreen])
     return;
 
-  if (animation_.IsShowing())
-    return;
-
   animation_.Reset(animation_start_value_);
   animation_.Show();
 }