Fix overflow/underflow in gfx geometry once and for all

ui/gfx/geometry/vector2d_unittest.cc

Index: ui/gfx/geometry/vector2d_unittest.cc
diff --git a/ui/gfx/geometry/vector2d_unittest.cc b/ui/gfx/geometry/vector2d_unittest.cc
index 98d75f22bf8db6f5842e53aa1261ed8c504905b0..4bdf24cba4acefd6109bafb7ca7d890d8933678c 100644
--- a/ui/gfx/geometry/vector2d_unittest.cc
+++ b/ui/gfx/geometry/vector2d_unittest.cc
@@ -249,4 +249,45 @@ TEST(Vector2dTest, ClampVector2dF) {
   EXPECT_EQ(Vector2dF(3.5f, 5.5f).ToString(), a.ToString());
 }
 
+TEST(Vector2dTest, IntegerOverflow) {
+  int int_max = std::numeric_limits<int>::max();
+  int int_min = std::numeric_limits<int>::min();
+
+  Vector2d max_vector(int_max, int_max);
+  Vector2d min_vector(int_min, int_min);
+  Vector2d test;
+
+  test = Vector2d();
+  test += Vector2d(int_max, int_max);
+  EXPECT_EQ(test, max_vector);
+
+  test = Vector2d();
+  test += Vector2d(int_min, int_min);
+  EXPECT_EQ(test, min_vector);
+
+  test = Vector2d(10, 20);
+  test += Vector2d(int_max, int_max);
+  EXPECT_EQ(test, max_vector);
+
+  test = Vector2d(-10, -20);
+  test += Vector2d(int_min, int_min);
+  EXPECT_EQ(test, min_vector);
+
+  test = Vector2d();
+  test -= Vector2d(int_max, int_max);
+  EXPECT_EQ(test, Vector2d(-int_max, -int_max));
+
+  test = Vector2d();
+  test -= Vector2d(int_min, int_min);
+  EXPECT_EQ(test, max_vector);
+
+  test = Vector2d(10, 20);
+  test -= Vector2d(int_min, int_min);
+  EXPECT_EQ(test, max_vector);
+
+  test = Vector2d(-10, -20);
+  test -= Vector2d(int_max, int_max);
+  EXPECT_EQ(test, min_vector);
+}
+
 }  // namespace gfx