Handle SkStream::rewind properly.

include/core/SkStream.h

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkStream_DEFINED
 #define SkStream_DEFINED
 
@@ skipping 78 matching lines @@
     SkScalar readScalar();
     size_t   readPackedUInt();
 
     /**
      *  Reconstitute an SkData object that was written to the stream
      *  using SkWStream::writeData().
      */
     SkData* readData();
 
 //SkStreamRewindable
-    /** Rewinds to the beginning of the stream. If this cannot be done, return false. */
+    /** Rewinds to the beginning of the stream. Returns true if the stream is known
+     *  to be at the beginning after this call returns.
+     */
     virtual bool rewind() { return false; }
 
     /** Duplicates this stream. If this cannot be done, returns NULL.
      *  The returned stream will be positioned at the beginning of its data.
      */
     virtual SkStreamRewindable* duplicate() const { return NULL; }
 
 //SkStreamSeekable
     /** Returns true if this stream can report it's current position. */
     virtual bool hasPosition() const { return false; }
@@ skipping 348 matching lines @@
     virtual void newline() SK_OVERRIDE;
 
 private:
     typedef SkWStream INHERITED;
 };
 
 // for now
 typedef SkFILEStream SkURLStream;
 
 #endif