private iterator to visit all resource cache entries

src/core/SkMaskCache.cpp

Index: src/core/SkMaskCache.cpp
diff --git a/src/core/SkMaskCache.cpp b/src/core/SkMaskCache.cpp
index 31a789fd389fa956d19b7b128501f54b7ba1057c..7dc4e4e3b880862e6c6be265b1af8c2f7ea7ff36 100644
--- a/src/core/SkMaskCache.cpp
+++ b/src/core/SkMaskCache.cpp
@@ -53,6 +53,10 @@ struct RRectBlurRec : public SkResourceCache::Rec {
 
     const Key& getKey() const override { return fKey; }
     size_t bytesUsed() const override { return sizeof(*this) + fValue.fData->size(); }
+    const char* getCategory() const override { return "rrect-blur"; }
+    SkDiscardableMemory* diagnostic_only_getDiscardable() const override {
+        return fValue.fData->diagnostic_only_getDiscardable();
+    }
 
     static bool Visitor(const SkResourceCache::Rec& baseRec, void* contextData) {
         const RRectBlurRec& rec = static_cast<const RRectBlurRec&>(baseRec);
@@ -144,6 +148,10 @@ struct RectsBlurRec : public SkResourceCache::Rec {
 
     const Key& getKey() const override { return fKey; }
     size_t bytesUsed() const override { return sizeof(*this) + fValue.fData->size(); }
+    const char* getCategory() const override { return "rects-blur"; }
+    SkDiscardableMemory* diagnostic_only_getDiscardable() const override {
+        return fValue.fData->diagnostic_only_getDiscardable();
+    }
 
     static bool Visitor(const SkResourceCache::Rec& baseRec, void* contextData) {
         const RectsBlurRec& rec = static_cast<const RectsBlurRec&>(baseRec);