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

ppapi/c/ppb_var.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_PPB_VAR_H_
 #define PPAPI_C_PPB_VAR_H_
 
 #include "ppapi/c/pp_bool.h"
 #include "ppapi/c/pp_instance.h"
 #include "ppapi/c/pp_macros.h"
@@ skipping 15 matching lines @@
  * @{
  */
 
 enum PP_ObjectProperty_Modifier {
   PP_OBJECTPROPERTY_MODIFIER_NONE       = 0,
   PP_OBJECTPROPERTY_MODIFIER_READONLY   = 1 << 0,
   PP_OBJECTPROPERTY_MODIFIER_DONTENUM   = 1 << 1,
   PP_OBJECTPROPERTY_MODIFIER_DONTDELETE = 1 << 2,
   PP_OBJECTPROPERTY_MODIFIER_HASVALUE   = 1 << 3
 };
+PP_COMPILE_ASSERT_ENUM_SIZE_IN_BYTES(PP_ObjectProperty_Modifier, 4);
 
 struct PP_ObjectProperty {
   struct PP_Var name;
   struct PP_Var value;
   struct PP_Var getter;
   struct PP_Var setter;
   uint32_t modifiers;
+
+  /** Ensure that this struct is 72 bytes wide by padding the end.  In some
+   *  compilers, PP_Var is 8-byte aligned, so those compilers align this struct
+   *  on 8-byte boundaries as well and pad it to 72 bytes even without this
+   *  padding attribute.  This padding makes its size consistent across
+   *  compilers.
+   */
+  int32_t padding;
 };
+PP_COMPILE_ASSERT_STRUCT_SIZE_IN_BYTES(PP_ObjectProperty, 72);
 
 /**
  * PPB_Var API
  *
  * JavaScript specification:
  *
  * When referencing JS specification, we will refer to ECMAScript, 5th edition,
  * and we will put section numbers in square brackets.
  *
  * Exception handling:
@@ skipping 236 matching lines @@
   result.setter = PP_MakeUndefined();
   result.modifiers = PP_OBJECTPROPERTY_MODIFIER_HASVALUE;
   return result;
 }
 
 /**
  * @}
  * End addtogroup PPB
  */
 #endif  // PPAPI_C_PPB_VAR_H_