Fix matrix interpolation between rotations of 180 degrees

ui/gfx/transform_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.
 
 // MSVC++ requires this to be set before any other includes to get M_PI.
 #define _USE_MATH_DEFINES
 
 #include "ui/gfx/transform.h"
 
 #include <stddef.h>
@@ skipping 727 matching lines @@
   for (size_t index = 0; index < arraysize(axes); ++index) {
     for (int i = -5; i < 15; ++i) {
       Transform to;
       to.RotateAbout(axes[index], 180.0);
       double t = i / 9.0;
       EXPECT_TRUE(to.Blend(from, t));
 
       // A 180 degree rotation is exactly opposite on the sphere, therefore
       // either great circle arc to it is equivalent (and numerical precision
       // will determine which is closer).  Test both directions.
-      Transform expected = from;
-      EXPECT_TRUE(MatricesAreNearlyEqual(expected, to))
+      Transform expected1;
+      expected1.RotateAbout(axes[index], 180.0 * t);
+      Transform expected2;
+      expected2.RotateAbout(axes[index], -180.0 * t);
+
+      EXPECT_TRUE(MatricesAreNearlyEqual(expected1, to) ||
+                  MatricesAreNearlyEqual(expected2, to))
           << "axis: " << index << ", i: " << i;
     }
   }
 }
 
 #if defined(_WIN64)
 // https://crbug.com/406574
 #define MAYBE_BlendScale DISABLED_BlendScale
 #else
 #define MAYBE_BlendScale BlendScale
@@ skipping 1971 matching lines @@
   EXPECT_FALSE(backface_invisible.IsBackFaceVisible());
 
   // A noise that is more than the tolerance should change the result.
   backface_invisible.matrix().set(0, 3, 1.f + (2 * noise));
   EXPECT_TRUE(backface_invisible.IsBackFaceVisible());
 }
 
 }  // namespace
 
 }  // namespace gfx