cc: Increment the ref count when assigning the SkImageFilter

cc/damage_tracker.cc

Index: cc/damage_tracker.cc
diff --git a/cc/damage_tracker.cc b/cc/damage_tracker.cc
index e10461d9aa771fbf8db685ce1e70b277b5e7c4f1..2bf5b8b03a96d5b91c851d5e2d4d5c64deab9ac9 100644
--- a/cc/damage_tracker.cc
+++ b/cc/damage_tracker.cc
@@ -48,7 +48,7 @@ static inline void expandDamageRectInsideRectWithFilters(gfx::RectF& damageRect,
     damageRect.Union(expandedDamageRect);
 }
 
-void DamageTracker::updateDamageTrackingState(const std::vector<LayerImpl*>& layerList, int targetSurfaceLayerID, bool targetSurfacePropertyChangedOnlyFromDescendant, const gfx::Rect& targetSurfaceContentRect, LayerImpl* targetSurfaceMaskLayer, const WebKit::WebFilterOperations& filters, SkImageFilter* filter)
+void DamageTracker::updateDamageTrackingState(const std::vector<LayerImpl*>& layerList, int targetSurfaceLayerID, bool targetSurfacePropertyChangedOnlyFromDescendant, const gfx::Rect& targetSurfaceContentRect, LayerImpl* targetSurfaceMaskLayer, const WebKit::WebFilterOperations& filters, const SkRefPtr<SkImageFilter>& filter)
 {
     //
     // This function computes the "damage rect" of a target surface, and updates the state