Fix blendToIdentity case in PerspectiveTransformOperation::blend

Source/platform/transforms/PerspectiveTransformOperation.cpp

 /*
  * Copyright (C) 2009 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "config.h"
 #include "platform/transforms/PerspectiveTransformOperation.h"
 
 #include "platform/animation/AnimationUtilities.h"
+#include "platform/transforms/IdentityTransformOperation.h"
 #include "wtf/MathExtras.h"
 
 using namespace std;
 
 namespace WebCore {
 
 PassRefPtr<TransformOperation> PerspectiveTransformOperation::blend(const TransformOperation* from, double progress, bool blendToIdentity)
 {
     if (from && !from->isSameType(*this))
         return this;
 
     if (blendToIdentity) {
-        double p = WebCore::blend(m_p, 1., progress); // FIXME: this seems wrong. https://bugs.webkit.org/show_bug.cgi?id=52700
+        if (progress == 1) {

[Julien - ping for review, 2014/01/10 13:41:41]

We don't put curly braces around single line if's.

+            return IdentityTransformOperation::create();
+        }
+        double p = m_p / (1 - progress);
         return PerspectiveTransformOperation::create(clampToPositiveInteger(p));
     }
 
     const PerspectiveTransformOperation* fromOp = static_cast<const PerspectiveTransformOperation*>(from);
 
     TransformationMatrix fromT;
     TransformationMatrix toT;
     fromT.applyPerspective(fromOp ? fromOp->m_p : 0);
     toT.applyPerspective(m_p);
     toT.blend(fromT, progress);
     TransformationMatrix::DecomposedType decomp;
     toT.decompose(decomp);
 
     if (decomp.perspectiveZ) {
         double val = -1.0 / decomp.perspectiveZ;
         return PerspectiveTransformOperation::create(clampToPositiveInteger(val));
     }
     return PerspectiveTransformOperation::create(0);
 }
 
 } // namespace WebCore