Fixed a few places where uninitialized memory could have been read

include/core/SkFlattenableBuffers.h

Index: include/core/SkFlattenableBuffers.h
diff --git a/include/core/SkFlattenableBuffers.h b/include/core/SkFlattenableBuffers.h
index 575dec8917661d3356f0e2035aecb0033c5dceeb..00cb77a8d35f1ba98e80493767c081764f4d51d0 100644
--- a/include/core/SkFlattenableBuffers.h
+++ b/include/core/SkFlattenableBuffers.h
@@ -154,6 +154,12 @@ public:
       */
     virtual bool validate(bool isValid);
 
+    /** This function returns true by default
+      * If isValidating() is true, it will return false if the internal error flag is set.
+      * Otherwise, it will return true.
+      */
+    virtual bool isValid() const { return true; }
+
 private:
     template <typename T> T* readFlattenableT();
     uint32_t fFlags;