Make the extra padding around VectorIconButtons configurable.

chrome/browser/ui/views/harmony/layout_delegate.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_UI_VIEWS_HARMONY_LAYOUT_DELEGATE_H_
 #define CHROME_BROWSER_UI_VIEWS_HARMONY_LAYOUT_DELEGATE_H_
 
 #include "ui/views/layout/grid_layout.h"
 
 class LayoutDelegate {
  public:
   enum class Metric {
     // Padding on the left and right side of a button's label.
     BUTTON_HORIZONTAL_PADDING,
+    // Extra margin added on all sides of a button's content.  This is only
+    // used for certain button types.
+    // TODO(pkasting): This should probably be touch-specific and needs to be
+    // considered more holistically.
+    BUTTON_MARGIN,
     // Default minimum width of a button.
     BUTTON_MINIMUM_WIDTH,
     // Margin between the edge of a dialog and the left, right, or bottom of a
     // contained button.
     DIALOG_BUTTON_MARGIN,
     // Minimum width of a dialog button.
     DIALOG_BUTTON_MINIMUM_WIDTH,
     // Spacing between a dialog button and the content above it.
     DIALOG_BUTTON_TOP_SPACING,
     // Horizontal or vertical margin between the edge of a dialog and the close
@@ skipping 65 matching lines @@
 
   // Returns the preferred width in DIPs for a dialog of the specified |width|.
   // May return 0 if the dialog has no preferred width.
   virtual int GetDialogPreferredWidth(DialogWidth width) const;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(LayoutDelegate);
 };
 
 #endif  // CHROME_BROWSER_UI_VIEWS_HARMONY_LAYOUT_DELEGATE_H_