ui: ToEnclosingRect(empty rect) should return an empty rect.

ui/gfx/rect_unittest.cc

 // Copyright (c) 2011 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 "base/basictypes.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/rect_conversions.h"
 #include "ui/gfx/skia_util.h"
 
@@ skipping 501 matching lines @@
     float y1;
     float w1;
     float h1;
     int x2; // target
     int y2;
     int w2;
     int h2;
   } tests [] = {
     { 0.0f, 0.0f, 0.0f, 0.0f,
       0, 0, 0, 0 },
+    { 5.5f, 5.5f, 0.0f, 0.0f,
+      5, 5, 0, 0 },
     { -1.5f, -1.5f, 3.0f, 3.0f,
       -2, -2, 4, 4 },
     { -1.5f, -1.5f, 3.5f, 3.5f,
       -2, -2, 4, 4 },
     { std::numeric_limits<float>::max(),
       std::numeric_limits<float>::max(),
       2.0f, 2.0f,
       std::numeric_limits<int>::max(),
       std::numeric_limits<int>::max(),
       0, 0 },
@@ skipping 217 matching lines @@
   EXPECT_EQ(Point(1, 6).ToString(), i.bottom_left().ToString());
   EXPECT_EQ(Point(4, 6).ToString(), i.bottom_right().ToString());
 
   EXPECT_EQ(PointF(1.1f, 2.1f).ToString(), f.origin().ToString());
   EXPECT_EQ(PointF(4.2f, 2.1f).ToString(), f.top_right().ToString());
   EXPECT_EQ(PointF(1.1f, 6.2f).ToString(), f.bottom_left().ToString());
   EXPECT_EQ(PointF(4.2f, 6.2f).ToString(), f.bottom_right().ToString());
 }
 
 }  // namespace gfx