Do not zero-initialize RawPtr.

Source/core/css/CSSBasicShapes.cpp

 /*
  * Copyright (C) 2011 Adobe Systems Incorporated. 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.
@@ skipping 60 matching lines @@
 {
     if ((offset.first()->getValueID() == CSSValueLeft && other.first()->getValueID() == CSSValueTop)
         || (offset.first()->getValueID() == CSSValueTop && other.first()->getValueID() == CSSValueLeft))
         return offset.second()->cssText();
     return offset.cssText();
 }
 
 static PassRefPtrWillBeRawPtr<CSSPrimitiveValue> buildSerializablePositionOffset(PassRefPtrWillBeRawPtr<CSSPrimitiveValue> offset, CSSValueID defaultSide)
 {
     CSSValueID side = defaultSide;
-    RefPtrWillBeRawPtr<CSSPrimitiveValue> amount;
+    RefPtrWillBeRawPtr<CSSPrimitiveValue> amount = nullptr;
 
     if (!offset) {
         side = CSSValueCenter;
     } else if (offset->isValueID()) {
         side = offset->getValueID();
     } else if (Pair* pair = offset->getPairValue()) {
         side = pair->first()->getValueID();
         amount = pair->second();
     } else {
         amount = offset;
@@ skipping 312 matching lines @@
     visitor->trace(m_left);
     visitor->trace(m_topLeftRadius);
     visitor->trace(m_topRightRadius);
     visitor->trace(m_bottomRightRadius);
     visitor->trace(m_bottomLeftRadius);
     CSSBasicShape::trace(visitor);
 }
 
 } // namespace WebCore