Fix layer shadow transform crash

bug:17180252

Change-Id: Ia648b8c98a217a3a4973917bf255d1397802cbbe
diff --git a/libs/hwui/DamageAccumulator.cpp b/libs/hwui/DamageAccumulator.cpp
index 054a164..420e331 100644
--- a/libs/hwui/DamageAccumulator.cpp
+++ b/libs/hwui/DamageAccumulator.cpp
@@ -214,7 +214,7 @@
     mHead->pendingDirty.join(left, top, right, bottom);
 }
 
-void DamageAccumulator::peekAtDirty(SkRect* dest) {
+void DamageAccumulator::peekAtDirty(SkRect* dest) const {
     *dest = mHead->pendingDirty;
 }