Generate thumbnails in the browser process.

chrome/common/render_messages_params.h

Index: chrome/common/render_messages_params.h
diff --git a/chrome/common/render_messages_params.h b/chrome/common/render_messages_params.h
index 09d18e075a9154ad367ce6d1f6051e4b81ebce64..9805a61e234a586b5077e958616d6f977b0376d0 100644
--- a/chrome/common/render_messages_params.h
+++ b/chrome/common/render_messages_params.h
@@ -341,6 +341,9 @@ struct ViewHostMsg_UpdateRect_Params {
   // The rectangular region to scroll.
   gfx::Rect scroll_rect;
 
+  // The scroll offset of the render view.
+  gfx::Size scroll_offset;
+
   // The regions of the bitmap (in view coords) that contain updated pixels.
   // In the case of scrolling, this includes the scroll damage rect.
   std::vector<gfx::Rect> copy_rects;