Fix for bug where composited rotate3d should SLERP

cc/animation/transform_operations_unittest.cc

 // Copyright 2013 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 <limits>
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_vector.h"
 #include "cc/animation/transform_operations.h"
 #include "cc/test/geometry_test_utils.h"
@@ skipping 423 matching lines @@
   gfx::Transform matrix_to;
   matrix_to.RotateAbout(gfx::Vector3dF(0, 1, 0), 175);
 
   gfx::Transform expected = matrix_to;
   expected.Blend(matrix_from, progress);
 
   EXPECT_TRANSFORMATION_MATRIX_EQ(
       expected, operations_to.Blend(operations_from, progress));
 }
 
+TEST(TransformOperationTest, RotationWithSlerpFromZeroDeg) {
+  TransformOperations operations_from;
+  operations_from.AppendRotate(0, 0, 1, 0);
+
+  TransformOperations operations_to;
+  operations_to.AppendRotate(0, 1, 0, 450);
+
+  SkMScalar progress = 0.5f;
+  gfx::Transform matrix_from;
+  matrix_from.RotateAbout(gfx::Vector3dF(0, 0, 1), 0);
+
+  gfx::Transform matrix_to;
+  matrix_to.RotateAbout(gfx::Vector3dF(0, 1, 0), 90);
+
+  gfx::Transform expected = matrix_to;
+  expected.Blend(matrix_from, progress);
+
+  EXPECT_TRANSFORMATION_MATRIX_EQ(
+      expected, operations_to.Blend(operations_from, progress));
+}
+
+TEST(TransformOperationTest, RotationWithoutSlerpFromZeroDeg) {
+  TransformOperations operations_from;
+  operations_from.AppendRotate(0, 0, 1, 0);
+
+  TransformOperations operations_to;
+  operations_to.AppendRotate(0, 0, 1, 450);
+
+  SkMScalar progress = 0.5f;
+  gfx::Transform expected;
+  expected.RotateAbout(gfx::Vector3dF(0, 0, 1), 225);
+
+  EXPECT_TRANSFORMATION_MATRIX_EQ(
+      expected, operations_to.Blend(operations_from, progress));
+}
+
 TEST(TransformOperationTest, BlendRotationFromIdentity) {
   ScopedVector<TransformOperations> identity_operations;
   GetIdentityOperations(&identity_operations);
 
   for (size_t i = 0; i < identity_operations.size(); ++i) {
     TransformOperations operations;
     operations.AppendRotate(0, 0, 1, 90);
 
     SkMScalar progress = 0.5f;
 
@@ skipping 1014 matching lines @@
 
   // Scale + Perspective can't.
   TransformOperations operations11;
   operations11.AppendScale(2.f, 2.f, 2.f);
   operations11.AppendPerspective(1.f);
   EXPECT_FALSE(operations11.ScaleComponent(&scale));
 }
 
 }  // namespace
 }  // namespace cc