Parametrize some more constants that will be changing in MD.

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

Index: chrome/browser/ui/views/tabs/tab_strip.h
diff --git a/chrome/browser/ui/views/tabs/tab_strip.h b/chrome/browser/ui/views/tabs/tab_strip.h
index e959e1969c6baa7ad409b5a336e91a81ca3527e3..f682871031a8409fbb372f121a78dff457a3c673 100644
--- a/chrome/browser/ui/views/tabs/tab_strip.h
+++ b/chrome/browser/ui/views/tabs/tab_strip.h
@@ -61,12 +61,6 @@ class TabStrip : public views::View,
   // restored windows.
   static const int kNewTabButtonVerticalOffset;
 
-  // The size of the new tab button must be hardcoded because we need to be
-  // able to lay it out before we are able to get its image from the
-  // ui::ThemeProvider.  It also makes sense to do this, because the size of the
-  // new tab button should not need to be calculated dynamically.
-  static const int kNewTabButtonAssetWidth;
-
   explicit TabStrip(TabStripController* controller);
   ~TabStrip() override;