For some vector icons, get the size from the vector definition.

ui/gfx/paint_vector_icon.h

 // Copyright 2015 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_GFX_PAINT_VECTOR_ICON_H_
 #define UI_GFX_PAINT_VECTOR_ICON_H_
 
 #include <stddef.h>
 
 #include "third_party/skia/include/core/SkColor.h"
 #include "ui/gfx/gfx_export.h"
 #include "ui/gfx/image/image_skia.h"
 
 namespace gfx {
 
 class Canvas;
 enum class VectorIconId;
 
 // Draws a vector icon identified by |id| onto |canvas| at (0, 0). |dip_size|
 // is the length of a single edge of the square icon, in device independent
 // pixels. |color| is used as the fill.
 GFX_EXPORT void PaintVectorIcon(Canvas* canvas,
                                 VectorIconId id,
                                 size_t dip_size,
                                 SkColor color);
 
-// Creates an ImageSkia which will render the icon on demand.
+// Creates an ImageSkia which will render the icon on demand. The size will come
+// from the .icon file (the 1x version, if multiple versions exist).
+GFX_EXPORT ImageSkia CreateVectorIcon(VectorIconId id,
+                                      SkColor color);
+
+// As above, but creates the image at the given size.
 GFX_EXPORT ImageSkia CreateVectorIcon(VectorIconId id,
                                       size_t dip_size,
                                       SkColor color);
 
 // As above, but also paints a badge defined by |badge_id| on top of the icon.
 // The badge uses the same canvas size and default color as the icon.
 GFX_EXPORT ImageSkia CreateVectorIconWithBadge(VectorIconId id,
                                                size_t dip_size,
                                                SkColor color,
                                                VectorIconId badge_id);
 
 #if defined(GFX_VECTOR_ICONS_UNSAFE) || defined(GFX_IMPLEMENTATION)
 // Takes a string of the format expected of .icon files and renders onto
 // a canvas. This should only be used as a debugging aid and should never be
 // used in production code.
 GFX_EXPORT ImageSkia CreateVectorIconFromSource(const std::string& source,
                                                 size_t dip_size,
                                                 SkColor color);
 #endif
 
 }  // namespace gfx
 
 #endif  // UI_GFX_PAINT_VECTOR_ICON_H_