Remove unused function

- GetNewTabButtonIdealX seems not used.

Change-Id: I01f27b70dcfd23b76ba1b3b70c083576143cf8f5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2494441
Commit-Queue: Connie Wan <connily@chromium.org>
Reviewed-by: Connie Wan <connily@chromium.org>
Cr-Commit-Position: refs/heads/master@{#820931}

chrome/browser/ui/views/tabs/tab_strip.h

@@ -490,10 +490,6 @@ class TabStrip : public views::View,
   // button and the frame grab area.
   int GetRightSideReservedWidth() const;
 
-  // Returns the X coordinate the new tab button should be placed at.  Requires
-  // |tabs_| to have correct ideal bounds.
-  int GetNewTabButtonIdealX() const;
-
   // Returns the last tab in the strip that's actually visible.  This will be
   // the actual last tab unless the strip is in the overflow node_data.
   const Tab* GetLastVisibleTab() const;