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

ppapi/c/dev/ppb_directory_reader_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_DIRECTORY_READER_DEV_H_
 #define PPAPI_C_DEV_PPB_DIRECTORY_READER_DEV_H_
 
 #include "ppapi/c/pp_bool.h"
 #include "ppapi/c/dev/pp_file_info_dev.h"
 #include "ppapi/c/pp_module.h"
 #include "ppapi/c/pp_resource.h"
 
 struct PP_CompletionCallback;
 
 struct PP_DirectoryEntry_Dev {
   PP_Resource file_ref;
   PP_FileType_Dev file_type;
+
+  /** Ensure that this struct is 16-bytes wide by padding the end.  Because
+   *  PP_Resource is an 8-byte type, some compilers align this struct on 8-byte
+   *  boundaries and pad it to 16 bytes even without @a padding.  This makes its
+   *  size consistent across compilers.
+   */
+  int32_t padding;
 };
+PP_COMPILE_ASSERT_STRUCT_SIZE_IN_BYTES(PP_DirectoryEntry_Dev, 16);
 
 #define PPB_DIRECTORYREADER_DEV_INTERFACE "PPB_DirectoryReader(Dev);0.2"
 
 struct PPB_DirectoryReader_Dev {
   // Creates a DirectoryReader for the given directory.  Upon success, the
   // corresponding directory is classified as "in use" by the resulting
   // DirectoryReader object until such time as the DirectoryReader object is
   // destroyed.
   PP_Resource (*Create)(PP_Resource directory_ref);
 
@@ skipping 17 matching lines @@
   //     ProcessDirectoryEntry(entry);
   //   }
   //   core_funcs->ReleaseResource(reader);
   //
   int32_t (*GetNextEntry)(PP_Resource directory_reader,
                           struct PP_DirectoryEntry_Dev* entry,
                           struct PP_CompletionCallback callback);
 };
 
 #endif  // PPAPI_C_DEV_PPB_DIRECTORY_READER_DEV_H_