add PurgeResourceCache to track leaks

src/core/SkResourceCache.h

Index: src/core/SkResourceCache.h
diff --git a/src/core/SkResourceCache.h b/src/core/SkResourceCache.h
index 93f2ca49e686d7ab2273b54ca0a8ca352cf8ab74..dacd62cedb914af54e07b7b805d7d6a9e243d970 100644
--- a/src/core/SkResourceCache.h
+++ b/src/core/SkResourceCache.h
@@ -106,6 +106,8 @@ public:
     static size_t SetSingleAllocationByteLimit(size_t);
     static size_t GetSingleAllocationByteLimit();
 
+    static void PurgeAll();
+
     /**
      * Use this allocator for bitmaps, so they can use ashmem when available.
      * Returns NULL if the ResourceCache has not been initialized with a DiscardableFactory.
@@ -167,6 +169,10 @@ public:
      */
     size_t setTotalByteLimit(size_t newLimit);
 
+    void purgeAll() {
+        this->purgeAsNeeded(true);
+    }
+
     SkBitmap::Allocator* allocator() const { return fAllocator; };
 
     /**
@@ -190,7 +196,7 @@ private:
     size_t  fSingleAllocationByteLimit;
     int     fCount;
 
-    void purgeAsNeeded();
+    void purgeAsNeeded(bool forcePurge = false);
 
     // linklist management
     void moveToHead(Rec*);