Use an InsetMetric instead of a constant for vector button padding.

ui/views/layout/layout_constants.h

Index: ui/views/layout/layout_constants.h
diff --git a/ui/views/layout/layout_constants.h b/ui/views/layout/layout_constants.h
index 98133510d1cb57289ddff493be26d8623a8c349f..2cc7aaf33dde53b56bef24f65f6528601c47832e 100644
--- a/ui/views/layout/layout_constants.h
+++ b/ui/views/layout/layout_constants.h
@@ -92,6 +92,9 @@ const int kMinimumButtonWidth = 48;
 // Minimum width of dialog buttons.
 constexpr int kDialogMinimumButtonWidth = 75;
 
+// Extra space around vector buttons to increase their event target size.
+constexpr int kVectorButtonExtraTouchSize = 4;

[sky, 2017/03/29 23:45:31]

If you add this constant here how do you prevent people from using it directly?
Don't you want code to use the InsetsMetric::VECTOR_IMAGE_BUTTON_PADDING?

[Peter Kasting, 2017/03/29 23:47:21]

I think the answer is "Allen's refactoring lands and this file goes away, and
the layout delegate becomes the only way to get at anything".

[Bret, 2017/03/29 23:52:00]

Right, since we're moving towards deleting this file I'd rather move constants
into it so they go away as part of the refactor.

+
 }  // namespace views
 
 #endif  // UI_VIEWS_LAYOUT_LAYOUT_CONSTANTS_H_