Add size_t bytesWritten() const to SkWStream.

src/utils/SkSHA1.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkSHA1_DEFINED
 #define SkSHA1_DEFINED
 
@@ skipping 11 matching lines @@
     SkSHA1();
 
     /** Processes input, adding it to the digest.
      *  Note that this treats the buffer as a series of uint8_t values.
      */
     virtual bool write(const void* buffer, size_t size) SK_OVERRIDE {
         update(reinterpret_cast<const uint8_t*>(buffer), size);
         return true;
     }
 
+    virtual size_t bytesWritten() const SK_OVERRIDE { return SkToSizeT(this->byteCount); }
+
     /** Processes input, adding it to the digest. Calling this after finish is undefined. */
     void update(const uint8_t* input, size_t length);
 
     struct Digest {
         uint8_t data[20];
     };
 
     /** Computes and returns the digest. */
     void finish(Digest& digest);
 
 private:
     // number of bytes, modulo 2^64
     uint64_t byteCount;
 
     // state (ABCDE)
     uint32_t state[5];
 
     // input buffer
     uint8_t buffer[64];
 };
 
 #endif