Fix NTB X coordinate for painting.

Things still look wrong even with this patch, because the Y coordinate is also
wrong; that's a deeper issue tracked in bug 866671.

Bug: 866665
Change-Id: I6a5f8fb159b3a70d71d1d17c904d2bd2d6d4fc6f
Reviewed-on: https://chromium-review.googlesource.com/1147085Reviewed-by: Allen Bauer <kylixrd@chromium.org>
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577558}

chrome/browser/ui/views/tabs/new_tab_button.cc

@@ -465,13 +465,13 @@ void NewTabButton::PaintFill(bool pressed,
       // The new tab background is mirrored in RTL mode, but the theme
       // background should never be mirrored. Mirror it here to compensate.
       float x_scale = 1.0f;
-      int x = GetMirroredX() + background_offset_.x();
-      const gfx::Size size = GetContentsBounds().size();
+      const gfx::Rect& contents_bounds = GetContentsBounds();
+      int x = GetMirroredX() + contents_bounds.x() + background_offset_.x();
       if (base::i18n::IsRTL()) {
         x_scale = -1.0f;
         // Offset by |width| such that the same region is painted as if there
         // was no flip.
-        x += size.width();
+        x += contents_bounds.width();
       }
 
       const bool succeeded = canvas->InitPaintFlagsForTiling(