Add ability to specify extra insets for a view via its border.

ui/views/border.h

 // Copyright (c) 2012 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 UI_VIEWS_BORDER_H_
 #define UI_VIEWS_BORDER_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 55 matching lines @@
                                                    int right);
 
   // Creates a border of the specified color, and specified thickness on each
   // side.
   static std::unique_ptr<Border> CreateSolidSidedBorder(int top,
                                                         int left,
                                                         int bottom,
                                                         int right,
                                                         SkColor color);
 
+  // Adds extra, unpainted insets to |border|. This is effectively equivalent to
+  // adding an EmptyBorder and then |border|. Example:

[sky, 2016/11/04 15:32:53]

optional:
I would take this second sentence to mean |border| is painted on the inside of
the EmptyBorder, which isn't quite what is happening. Maybe something like:

Creates a new border that draws |border| and adds additional padding. This is
equivalent to changing the insets of |border| without changing how or what it
paints.

I favor a name of WrapBorderWithPadding, but I realize naming is hard and leave
it to you. I would actually prefer Create in the name, but it's hard to get
something that sounds reasonable.

[Evan Stade, 2016/11/04 15:50:16]

ok
CreatePaddedBorder?

while we're at it, how can we make this less verbose:

  views::Border::CreateRoundedRectBorder

Options that come to mind:

a) views::CreateRoundedRectBorder (promote to standalone static fn in views
namespace)
b) views::Border::CreateRoundedRect (remove trailing "Border")

+  //
+  // view->SetBorder(Border::AddInteriorPadding(
+  //                     Border::CreateSolidBorder(1, SK_ColorRED),
+  //                     gfx::Insets(2, 0, 0, 0)));
+  //
+  // yields a single dip red border and an additional 2dip of unpainted padding
+  // above the view content (below the border).
+  static std::unique_ptr<Border> AddInteriorPadding(
+      std::unique_ptr<Border> border,
+      const gfx::Insets& insets);
+
   // Creates a Border from the specified Painter.
   // |insets| define size of an area allocated for a Border.
   static std::unique_ptr<Border> CreateBorderPainter(
       std::unique_ptr<Painter> painter,
       const gfx::Insets& insets);
 
   // Renders the border for the specified view.
   virtual void Paint(const View& view, gfx::Canvas* canvas) = 0;
 
   // Returns the border insets.
   virtual gfx::Insets GetInsets() const = 0;
 
   // Returns the minimum size this border requires.  Note that this may not be
   // the same as the insets.  For example, a Border may paint images to draw
   // some graphical border around a view, and this would return the minimum size
   // such that these images would not be clipped or overlapping -- but the
   // insets may be larger or smaller, depending on how the view wanted its
   // content laid out relative to these images.
   virtual gfx::Size GetMinimumSize() const = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(Border);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_BORDER_H_