gfx: Make conversions from Size to SizeF be explicit.

ui/gfx/geometry/rect_f.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_GFX_GEOMETRY_RECT_F_H_
 #define UI_GFX_GEOMETRY_RECT_F_H_
 
 #include <iosfwd>
 #include <string>
 
@@ skipping 15 matching lines @@
  public:
   RectF() {}
   RectF(float width, float height) : size_(width, height) {}
   RectF(float x, float y, float width, float height)
       : origin_(x, y), size_(width, height) {}
   explicit RectF(const SizeF& size) : size_(size) {}
   RectF(const PointF& origin, const SizeF& size)
       : origin_(origin), size_(size) {}
 
   explicit RectF(const Rect& r)
-      // TODO(danakj): Change these to checked_cast?
       : RectF(static_cast<float>(r.x()),
               static_cast<float>(r.y()),
               static_cast<float>(r.width()),
               static_cast<float>(r.height())) {}
 
 #if defined(OS_MACOSX)
   explicit RectF(const CGRect& r);
   // Construct an equivalent CoreGraphics object.
   CGRect ToCGRect() const;
 #endif
@@ skipping 188 matching lines @@
 GFX_EXPORT RectF BoundingRect(const PointF& p1, const PointF& p2);
 
 // This is declared here for use in gtest-based unit tests but is defined in
 // the gfx_test_support target. Depend on that to use this in your unit test.
 // This should not be used in production code - call ToString() instead.
 void PrintTo(const RectF& rect, ::std::ostream* os);
 
 }  // namespace gfx
 
 #endif  // UI_GFX_GEOMETRY_RECT_F_H_