gfx: Make conversions from Size to SizeF be explicit.

ui/gfx/geometry/size_unittest.cc

 // 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.
 
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/gfx/geometry/size.h"
 #include "ui/gfx/geometry/size_conversions.h"
 #include "ui/gfx/geometry/size_f.h"
 
 namespace gfx {
 
 namespace {
 
 int TestSizeF(const SizeF& s) {
   return s.width();
 }
 
 }  // namespace
 
 TEST(SizeTest, ToSizeF) {
-  // Check that implicit conversion from integer to float compiles.
+  // Check that explicit conversion from integer to float compiles.
   Size a(10, 20);
-  float width = TestSizeF(a);
+  float width = TestSizeF(gfx::SizeF(a));
   EXPECT_EQ(width, a.width());
 
   SizeF b(10, 20);
 
-  EXPECT_EQ(a, b);
-  EXPECT_EQ(b, a);
+  EXPECT_EQ(b, gfx::SizeF(a));
 }
 
 TEST(SizeTest, ToFlooredSize) {
   EXPECT_EQ(Size(0, 0), ToFlooredSize(SizeF(0, 0)));
   EXPECT_EQ(Size(0, 0), ToFlooredSize(SizeF(0.0001f, 0.0001f)));
   EXPECT_EQ(Size(0, 0), ToFlooredSize(SizeF(0.4999f, 0.4999f)));
   EXPECT_EQ(Size(0, 0), ToFlooredSize(SizeF(0.5f, 0.5f)));
   EXPECT_EQ(Size(0, 0), ToFlooredSize(SizeF(0.9999f, 0.9999f)));
 
   EXPECT_EQ(Size(10, 10), ToFlooredSize(SizeF(10, 10)));
@@ skipping 77 matching lines @@
   EXPECT_EQ(SizeF(8.5f, 10.5f).ToString(), a.ToString());
   a.SetToMin(SizeF(11.5f, 9.5f));
   EXPECT_EQ(SizeF(8.5f, 9.5f).ToString(), a.ToString());
   a.SetToMin(SizeF(7.5f, 11.5f));
   EXPECT_EQ(SizeF(7.5f, 9.5f).ToString(), a.ToString());
   a.SetToMin(SizeF(3.5f, 5.5f));
   EXPECT_EQ(SizeF(3.5f, 5.5f).ToString(), a.ToString());
 }
 
 }  // namespace gfx