add optoinal bytesRead argument (output) to playback()



git-svn-id: http://skia.googlecode.com/svn/trunk@1400 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/include/pipe/SkGPipe.h b/include/pipe/SkGPipe.h
index 0ca66ab..897766f 100644
--- a/include/pipe/SkGPipe.h
+++ b/include/pipe/SkGPipe.h
@@ -36,7 +36,7 @@
 
     // data must be 4-byte aligned
     // length must be a multiple of 4
-    Status playback(const void* data, size_t length);
+    Status playback(const void* data, size_t length, size_t* bytesRead = NULL);
 
 private:
     SkCanvas*           fCanvas;