Make a new test to enforce the sizes of all structs and enums in the C API....

ppapi/c/dev/ppb_scrollbar_dev.h

 // Copyright (c) 2010 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 PPAPI_C_DEV_PPB_SCROLLBAR_DEV_H_
 #define PPAPI_C_DEV_PPB_SCROLLBAR_DEV_H_
 
 #include "ppapi/c/pp_bool.h"
 #include "ppapi/c/pp_instance.h"
 #include "ppapi/c/pp_resource.h"
 #include "ppapi/c/pp_stdint.h"
 
 struct PP_Rect;
 
 typedef enum {
   PP_SCROLLBY_PIXEL = 0,
   PP_SCROLLBY_LINE = 1,
   PP_SCROLLBY_PAGE = 2,
   PP_SCROLLBY_DOCUMENT = 3
 } PP_ScrollBy_Dev;
+PP_COMPILE_ASSERT_SIZE_IN_BYTES(PP_ScrollBy_Dev, 4);
 
 #define PPB_SCROLLBAR_DEV_INTERFACE "PPB_Scrollbar(Dev);0.2"
 
 // The interface for a scrollbar.  A scrollbar is a widget, so the functions
 // in PPB_Widget can also be used with scrollbar objects.
 struct PPB_Scrollbar_Dev {
   // Create a new scrollbar.  Returns 0 if the instance is invalid.
   PP_Resource (*Create)(PP_Instance instance,
                         PP_Bool vertical);
 
@@ skipping 23 matching lines @@
 
   // Scroll by "multiplier" pixels/lines/pages units.  Positive values are
   // forward and negative are backward.  If "unit" is document then any positive
   // value goes to the end while any negative value goes to the beginning.
   void (*ScrollBy)(PP_Resource scrollbar,
                    PP_ScrollBy_Dev unit,
                    int32_t multiplier);
 };
 
 #endif  // PPAPI_C_DEV_PPB_SCROLLBAR_DEV_H_