Fix overflow/underflow in gfx geometry once and for all

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 {
@@ skipping 104 matching lines @@
   a.SetToMin(SizeF(8.5f, 10.5f));
   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());
 }
 
+TEST(SizeTest, Enlarge) {
+  Size test(3, 4);
+  test.Enlarge(5, -8);
+  EXPECT_EQ(test, Size(8, -4));
+}
+
+TEST(SizeTest, IntegerOverflow) {
+  int int_max = std::numeric_limits<int>::max();
+  int int_min = std::numeric_limits<int>::min();
+
+  Size max_size(int_max, int_max);
+  Size min_size(int_min, int_min);
+  Size test;
+
+  test = Size();
+  test.Enlarge(int_max, int_max);
+  EXPECT_EQ(test, max_size);
+
+  test = Size();
+  test.Enlarge(int_min, int_min);
+  EXPECT_EQ(test, min_size);
+
+  test = Size(10, 20);
+  test.Enlarge(int_max, int_max);
+  EXPECT_EQ(test, max_size);
+
+  test = Size(-10, -20);
+  test.Enlarge(int_min, int_min);
+  EXPECT_EQ(test, min_size);
+}
+
 }  // namespace gfx