ps test.

cc/base/index_rect.cc

 // Copyright 2016 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 "cc/base/index_rect.h"
 
 #include <algorithm>
 
 #include "base/strings/stringprintf.h"
+#include "ui/gfx/geometry/safe_integer_conversions.h"
 
 namespace cc {
 
 void IndexRect::ClampTo(const IndexRect& other) {
   left_ = std::max(left_, other.left());
   top_ = std::max(top_, other.top());
   right_ = std::min(right_, other.right());
   bottom_ = std::min(bottom_, other.bottom());
 }
 
 bool IndexRect::Contains(int index_x, int index_y) const {
   return index_x >= left_ && index_x <= right_ && index_y >= top_ &&
          index_y <= bottom_;
 }
 
+void IndexRect::Inset(int left, int right, int top, int bottom) {
+  left_ = gfx::SafeAdd(left_, left);
+  right_ = gfx::SafeSubtract(right_, right);
+  top_ = gfx::SafeAdd(top_, top);
+  bottom_ = gfx::SafeSubtract(bottom_, bottom);
+}
+
 std::string IndexRect::ToString() const {
   return base::StringPrintf("%d,%d,%d,%d", left(), right(), top(), bottom());
 }
 
 }  // namespace cc