Avoid integer overflow in LayoutUnit's unary minus operator

third_party/WebKit/Source/platform/LayoutUnitTest.cpp

 /*
  * Copyright (c) 2012, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 238 matching lines @@
 
 TEST(LayoutUnitTest, LayoutUnitFloatOverflow)
 {
     // These should overflow to the max/min according to their sign.
     EXPECT_EQ(intMaxForLayoutUnit, LayoutUnit(176972000.0f).toInt());
     EXPECT_EQ(intMinForLayoutUnit, LayoutUnit(-176972000.0f).toInt());
     EXPECT_EQ(intMaxForLayoutUnit, LayoutUnit(176972000.0).toInt());
     EXPECT_EQ(intMinForLayoutUnit, LayoutUnit(-176972000.0).toInt());
 }
 
+TEST(LayoutUnitTest, UnaryMinus)
+{
+    EXPECT_EQ(LayoutUnit(), -LayoutUnit());
+    EXPECT_EQ(LayoutUnit(999), -LayoutUnit(-999));
+    EXPECT_EQ(LayoutUnit(-999), -LayoutUnit(999));
+
+    LayoutUnit negativeMax;
+    negativeMax.setRawValue(LayoutUnit::min().rawValue() + 1);
+    EXPECT_EQ(negativeMax, -LayoutUnit::max());
+    EXPECT_EQ(LayoutUnit::max(), -negativeMax);
+
+    // -LayoutUnit::min() is saturated to LayoutUnit::max()
+    EXPECT_EQ(LayoutUnit::max(), -LayoutUnit::min());
+}
+
 } // namespace blink