[iOS] Don't reset fullscreen state if the toolbar height doesn't change.

Bug: 794478
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: Id37c0070d19c0b393903d121e58753a5e0be9aea
Reviewed-on: https://chromium-review.googlesource.com/835648Reviewed-by: Sergio Collazos <sczs@chromium.org>
Commit-Queue: Kurt Horimoto <kkhorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#525267}

ios/chrome/browser/ui/fullscreen/fullscreen_model.mm

@@ -65,6 +65,8 @@ void FullscreenModel::AnimationEndedWithProgress(CGFloat progress) {
 }
 
 void FullscreenModel::SetToolbarHeight(CGFloat toolbar_height) {
+  if (AreCGFloatsEqual(toolbar_height_, toolbar_height))
+    return;
   DCHECK_GE(toolbar_height, 0.0);
   toolbar_height_ = toolbar_height;
   ResetForNavigation();