[iOS] Remove one tab model observer helper method from BVC.

The CL removes a method that was functionally a no-op.

Change-Id: I721a3f573253df4728dd9cc18ff484c56b52488a
Reviewed-on: https://chromium-review.googlesource.com/c/1317860
Commit-Queue: Mark Cogan <marq@chromium.org>
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606043}

ios/chrome/browser/ui/browser_view_controller.mm

@@ -4924,13 +4924,12 @@ applicationCommandEndpoint:(id<ApplicationCommands>)applicationCommandEndpoint {
     }
   };
 
-  self.inNewTabAnimation = YES;
-  if (!background) {
-    [self animateNewTab:tab
-        inForegroundWithCompletion:startVoiceSearchIfNecessary];
+  if (background) {
+    self.inNewTabAnimation = NO;
   } else {
+    self.inNewTabAnimation = YES;
     [self animateNewTab:tab
-        inBackgroundWithCompletion:startVoiceSearchIfNecessary];
+        inForegroundWithCompletion:startVoiceSearchIfNecessary];
   }
 }
 
@@ -5112,11 +5111,6 @@ applicationCommandEndpoint:(id<ApplicationCommands>)applicationCommandEndpoint {
       toTabGridButtonWithCompletion:completionBlock];
 }
 
-- (void)animateNewTab:(Tab*)tab
-    inBackgroundWithCompletion:(ProceduralBlock)completion {
-  self.inNewTabAnimation = NO;
-}
-
 #pragma mark - InfobarPositioner
 
 - (UIView*)parentView {