Allow GrGpuResources' unique keys to be changed.

include/gpu/GrContext.h

Index: include/gpu/GrContext.h
diff --git a/include/gpu/GrContext.h b/include/gpu/GrContext.h
index 712eeb83348f99f9dcc34290813bcd5de518e434..846cd0f1118fa492da7633d8fec5b84d68b87568 100644
--- a/include/gpu/GrContext.h
+++ b/include/gpu/GrContext.h
@@ -169,10 +169,11 @@ public:
      */
     void purgeAllUnlockedResources();
 
-    /** Sets a unique key on the resource. The resource must not already have a unique key and the
-     *  key must not already be in use for this to succeed.
+    /**
+     * Sets a unique key on the resource. Upon key collision this resource takes the place of the
+     * previous resource that had the key.
      */
-    bool addResourceToCache(const GrUniqueKey&, GrGpuResource*);
+    void addResourceToCache(const GrUniqueKey&, GrGpuResource*);
 
     /**
      * Finds a resource in the cache, based on the specified key. This is intended for use in