Adding error checks to SkRBuffer

include/core/SkFlattenableBuffers.h

 
 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkFlattenableBuffers_DEFINED
 #define SkFlattenableBuffers_DEFINED
@@ skipping 126 matching lines @@
         return point;
     }
 
     SkData* readByteArrayAsData() {
         size_t len = this->getArrayCount();
         void* buffer = sk_malloc_throw(len);
         (void)this->readByteArray(buffer, len);
         return SkData::NewFromMalloc(buffer, len);
     }
 
-    virtual void validate(bool isValid) {}
+    /** This function validates that the isValid input parameter is true
+      * If isValidating() is false, then true is always returned
+      * If isValidating() is true, then true is returned until validate() is called with isValid
+      * set to false. When isValid is false, an error flag will be set internally and, from that
+      * point on, validate() will return false. The error flag cannot be unset.
+      *
+      * @param isValid result of a test that is expected to be true
+      */
+    virtual bool validate(bool isValid);
 
 private:
     template <typename T> T* readFlattenableT();
     uint32_t fFlags;
 };
 
 ///////////////////////////////////////////////////////////////////////////////
 
 class SkFlattenableWriteBuffer {
 public:
@@ skipping 66 matching lines @@
     }
 
 protected:
     // A helper function so that each subclass does not have to be a friend of SkFlattenable
     void flattenObject(const SkFlattenable* obj, SkFlattenableWriteBuffer& buffer);
 
     uint32_t fFlags;
 };
 
 #endif