Don't decompose retargeted rotate() transform transitions

third_party/WebKit/Source/platform/transforms/RotateTransformOperation.cpp

 /*
  * Copyright (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  *
  */
 
 #include "platform/transforms/RotateTransformOperation.h"
 
+#include "platform/animation/AnimationUtilities.h"
+
 namespace blink {
 
 bool RotateTransformOperation::operator==(const TransformOperation& other) const
 {
     if (!isSameType(other))
         return false;
     const Rotation& otherRotation = toRotateTransformOperation(other).m_rotation;
     return m_rotation.axis == otherRotation.axis && m_rotation.angle == otherRotation.angle;
 }
 
 bool RotateTransformOperation::getCommonAxis(const RotateTransformOperation* a, const RotateTransformOperation* b, FloatPoint3D& resultAxis, double& resultAngleA, double& resultAngleB)
 {
     return Rotation::getCommonAxis(a ? a->m_rotation : Rotation(), b ? b->m_rotation : Rotation(), resultAxis, resultAngleA, resultAngleB);
 }
 
 PassRefPtr<TransformOperation> RotateTransformOperation::blend(const TransformOperation* from, double progress, bool blendToIdentity)
 {
     if (from && !from->isSameType(*this))
         return this;
 
     if (blendToIdentity)
         return RotateTransformOperation::create(Rotation(axis(), angle() * (1 - progress)), m_type);
 
     // Optimize for single axis rotation
     if (!from)
         return RotateTransformOperation::create(Rotation(axis(), angle() * progress), m_type);
 
-    return RotateTransformOperation::create(
-        Rotation::slerp(toRotateTransformOperation(*from).m_rotation, m_rotation, progress), Rotate3D);
+    const RotateTransformOperation& fromRotate = toRotateTransformOperation(*from);
+    if (type() == Rotate3D) {
+        return RotateTransformOperation::create(
+            Rotation::slerp(fromRotate.m_rotation, m_rotation, progress), Rotate3D);
+    }
+
+    ASSERT(axis() == fromRotate.axis());
+    return RotateTransformOperation::create(Rotation(axis(), blink::blend(fromRotate.angle(), angle(), progress)), m_type);
 }
 
 bool RotateTransformOperation::canBlendWith(const TransformOperation& other) const
 {
     return other.isSameType(*this);
 }
 
 } // namespace blink