Basic windowless plugins, try 2.

base/gfx/native_widget_types.h

 // Copyright (c) 2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_GFX_NATIVE_WIDGET_TYPES_H_
 #define BASE_GFX_NATIVE_WIDGET_TYPES_H_
 
 #include "base/basictypes.h"
 #include "build/build_config.h"
 
@@ skipping 31 matching lines @@
 @class NSWindow;
 @class NSTextField;
 #else
 class NSView;
 class NSWindow;
 class NSTextField;
 #endif  // __OBJC__
 #elif defined(OS_LINUX)
 typedef struct _GtkWidget GtkWidget;
 typedef struct _GtkWindow GtkWindow;
+typedef struct _cairo_surface cairo_surface_t;
 #endif
 
 namespace gfx {
 
 #if defined(OS_WIN)
 typedef HWND NativeView;
 typedef HWND NativeWindow;
 typedef HWND NativeEditView;
 typedef HDC NativeDrawingContext;
 #elif defined(OS_MACOSX)
 typedef NSView* NativeView;
 typedef NSWindow* NativeWindow;
 typedef NSTextField* NativeEditView;
 typedef CGContext* NativeDrawingContext;
 #elif defined(OS_LINUX)
 typedef GtkWidget* NativeView;
 typedef GtkWindow* NativeWindow;
 typedef GtkWidget* NativeEditView;
-typedef void *NativeDrawingContext; // TODO(port): update for Gtk
-#else  // null port.
-#error No known OS defined
+typedef cairo_surface_t* NativeDrawingContext;
 #endif
 
 // Note: for test_shell we're packing a pointer into the NativeViewId. So, if
 // you make it a type which is smaller than a pointer, you have to fix
 // test_shell.
 //
 // See comment at the top of the file for usage.
 typedef intptr_t NativeViewId;
 
 // Convert a NativeViewId to a NativeView. At the moment, we assume that the
@@ skipping 10 matching lines @@
 // NativeView == HWND).
 // TODO(port): figure out what ids are going to be and implement this function
 // This is only to be called in the browser process.
 static inline NativeViewId IdFromNativeView(NativeView view) {
   return reinterpret_cast<NativeViewId>(view);
 }
 
 }  // namespace gfx
 
 #endif  // BASE_GFX_NATIVE_WIDGET_TYPES_H_