Update a result vector when sampling animation effects.

Source/core/animation/InterpolationEffect.cpp

 // Copyright 2014 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 "config.h"
 #include "core/animation/InterpolationEffect.h"
 
 namespace blink {
 
-PassOwnPtrWillBeRawPtr<WillBeHeapVector<RefPtrWillBeMember<Interpolation> > > InterpolationEffect::getActiveInterpolations(double fraction, double iterationDuration) const
+void InterpolationEffect::getActiveInterpolations(double fraction, double iterationDuration, OwnPtrWillBeRawPtr<WillBeHeapVector<RefPtrWillBeMember<Interpolation>>>& result) const
 {
+    if (!result)
+        result = adoptPtrWillBeNoop(new WillBeHeapVector<RefPtrWillBeMember<Interpolation> >());
 
-    WillBeHeapVector<RefPtrWillBeMember<Interpolation> >* result = new WillBeHeapVector<RefPtrWillBeMember<Interpolation> >();
+    size_t existingSize = result->size();
+    size_t resultIndex = 0;
 
     for (size_t i = 0; i < m_interpolations.size(); ++i) {
         const InterpolationRecord* record = m_interpolations[i].get();
         if (fraction >= record->m_applyFrom && fraction < record->m_applyTo) {
             RefPtrWillBeRawPtr<Interpolation> interpolation = record->m_interpolation;
             double localFraction = (fraction - record->m_start) / (record->m_end - record->m_start);
             if (record->m_easing)
                 localFraction = record->m_easing->evaluate(localFraction, accuracyForDuration(iterationDuration));
             interpolation->interpolate(0, localFraction);
-            result->append(interpolation);
+            if (resultIndex < existingSize)
+                (*result)[resultIndex++] = interpolation;
+            else
+                result->append(interpolation);
         }
     }
-
-    return adoptPtrWillBeNoop(result);
+    if (resultIndex < existingSize)
+        result->shrink(resultIndex);
 }
 
 void InterpolationEffect::InterpolationRecord::trace(Visitor* visitor)
 {
     visitor->trace(m_interpolation);
 }
 
 void InterpolationEffect::trace(Visitor* visitor)
 {
 #if ENABLE_OILPAN
     visitor->trace(m_interpolations);
 #endif
 }
 
 }