This CL adds client.toDataURL which gets the contents...

core/cross/bitmap.h

 /*
  * Copyright 2009, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 224 matching lines @@
   bool LoadFromRawData(RawData *raw_data,
                        image::ImageFileType file_type,
                        bool generate_mipmaps);
 
   // Flips a bitmap vertically in place.
   // This is needed instead of just using DrawImage because flipping DXT formats
   // using generic algorithms would be lossy and extremely slow to reconvert
   // from a flippable format back to a DXT format.
   void FlipVertically();
 
-  // Saves to a PNG file. The image must be of the ARGB8 format, be a 2D image
-  // with no mip-maps (only the base level).
-  // Parameters:
-  //   filename: the name of the file to into.
+  // Returns the contents of the bitmap as a data URL
   // Returns:
-  //   true if successful.
-  bool SaveToPNGFile(const char* filename);
+  //   A data url that represents the content of the bitmap.
+  String ToDataURL();
 
   // Checks that the alpha channel for the entire bitmap is 1.0
   bool CheckAlphaIsOne() const;
 
   // Copy pixels from source bitmap. Scales if the width and height of source
   // and dest do not match.
   // Parameters:
   //   source_img: source bitmap which would be drawn.
   //   source_x: x-coordinate of the starting pixel in the source image.
   //   source_x: y-coordinate of the starting pixel in the source image.
@@ skipping 141 matching lines @@
  public:
   explicit BitmapDXT5(ServiceLocator* service_locator);
 
  private:
   DISALLOW_COPY_AND_ASSIGN(BitmapDXT5);
 };
 
 }  // namespace o3d
 
 #endif  // O3D_CORE_CROSS_BITMAP_H_