views: support dialog width snapping once and for all

ui/views/layout/layout_provider.h

 // Copyright 2017 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_LAYOUT_LAYOUT_PROVIDER_H_
 #define UI_VIEWS_LAYOUT_LAYOUT_PROVIDER_H_
 
 #include "base/macros.h"
 #include "ui/gfx/geometry/insets.h"
 #include "ui/views/style/typography_provider.h"
@@ skipping 65 matching lines @@
   virtual gfx::Insets GetInsetsMetric(int metric) const;
 
   // Returns the distance metric between elements according to the given
   // enumeration element.
   virtual int GetDistanceMetric(int metric) const;
 
   // Returns the TypographyProvider, used to configure text properties such as
   // font, weight, color, size, and line height. Never null.
   virtual const TypographyProvider& GetTypographyProvider() const;
 
+  // Returns the actual width to use for a dialog that requires at least
+  // |min_width|.
+  virtual int GetSnappedDialogWidth(int min_width) const;
+
  private:
   DefaultTypographyProvider typography_provider_;
 
   DISALLOW_COPY_AND_ASSIGN(LayoutProvider);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_LAYOUT_LAYOUT_PROVIDER_H_