Add wrapper container for a vector of OwnPtr<T>

cc/CCLayerTreeHostCommon.h

Index: cc/CCLayerTreeHostCommon.h
diff --git a/cc/CCLayerTreeHostCommon.h b/cc/CCLayerTreeHostCommon.h
index d8710e95e5a0a2c52f07ecaaa429fc75b7ebf7e9..65cf7685d2a2f25eab1ecf6be7a807dd9897fb0c 100644
--- a/cc/CCLayerTreeHostCommon.h
+++ b/cc/CCLayerTreeHostCommon.h
@@ -7,6 +7,7 @@
 
 #include "IntRect.h"
 #include "IntSize.h"
+#include "cc/own_ptr_vector.h"
 #include <public/WebTransformationMatrix.h>
 #include <wtf/RefPtr.h>
 #include <wtf/Vector.h>
@@ -36,6 +37,16 @@ public:
     // from the given root layer (including mask and replica layers).
     template<typename LayerType> static LayerType* findLayerInSubtree(LayerType* rootLayer, int layerId);
 
+    static LayerChromium* getChildAsRawPtr(const Vector<RefPtr<LayerChromium> >& children, size_t index)
+    {
+        return children[index].get();
+    }
+
+    static CCLayerImpl* getChildAsRawPtr(const OwnPtrVector<CCLayerImpl>& children, size_t index)
+    {
+        return children[index];
+    }
+
     struct ScrollUpdateInfo {
         int layerId;
         IntSize scrollDelta;
@@ -74,7 +85,7 @@ LayerType* CCLayerTreeHostCommon::findLayerInSubtree(LayerType* rootLayer, int l
         return rootLayer->replicaLayer();
 
     for (size_t i = 0; i < rootLayer->children().size(); ++i) {
-        if (LayerType* found = findLayerInSubtree(rootLayer->children()[i].get(), layerId))
+        if (LayerType* found = findLayerInSubtree(getChildAsRawPtr(rootLayer->children(), i), layerId))
             return found;
     }
     return 0;