Add the xrender backend to the window manager.

image_container.h

Index: image_container.h
diff --git a/image_container.h b/image_container.h
index c56f86b2db50d3be6367bedf37b66121a435ad07..b953fc293d58e81c9d1d9c7aff61a061c89c9210 100644
--- a/image_container.h
+++ b/image_container.h
@@ -10,6 +10,7 @@
 #include "base/basictypes.h"
 #include "base/logging.h"
 #include "base/scoped_ptr.h"
+#include "window_manager/geometry.h"
 #include "window_manager/image_enums.h"
 
 namespace window_manager {
@@ -40,6 +41,7 @@ class ImageContainer {
   uint8_t* data() const { return data_; }
   size_t width() const { return width_; }
   size_t height() const { return height_; }
+  Size size() const { return Size(width_,height_); }
 
   // Return stride in bytes of a row of pixels in the image data.
   size_t stride() const {