A second attempt at forcing 8-byte alignment of the time stamp....

ppapi/c/pp_input_event.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_PP_INPUT_EVENT_H_
 #define PPAPI_C_PP_INPUT_EVENT_H_
 
 /**
  * @file
  * Defines the API ...
@@ skipping 132 matching lines @@
   uint32_t modifier;
 
   float delta_x;
   float delta_y;
   float wheel_ticks_x;
   float wheel_ticks_y;
 
   PP_Bool scroll_by_page;
 };
 
-/* Ensure the elements of the struct (especially the time_stamp) are aligned on
-   8-byte boundaries, since some compilers align doubles on 8-byte boundaries
-   for 32-bit x86, and some align on 4-byte boundaries. */
-#pragma pack(push, 8)
 struct PP_InputEvent {
   /** Identifies the type of the event. */
   PP_InputEvent_Type type;
 
+  /* Ensure the time_stamp is aligned on an 8-byte boundary relative to the
+     start of the struct. Some compilers align doubles on 8-byte boundaries
+     for 32-bit x86, and some align on 4-byte boundaries. */
+  int32_t padding;
+
   /**
    * When this event was generated. This is not relative to any particular
    * epoch, the most you can do is compare time stamps.
    */
   PP_TimeTicks time_stamp;
 
   /** Event-specific data. */
   union {
     struct PP_InputEvent_Key key;
     struct PP_InputEvent_Character character;
     struct PP_InputEvent_Mouse mouse;
     struct PP_InputEvent_Wheel wheel;
 
     /**
      * Allows new events to be added without changing the size of this
      * struct.
      */
     char padding[64];
   } u;
 };
-#pragma pack(pop)
-/* TODO(dmichael):  Figure out why the input event is not 80 bytes wide on Mac.
 PP_COMPILE_ASSERT_STRUCT_SIZE_IN_BYTES(PP_InputEvent, 80);
- */
 
 /**
  * @}
  * End of addtogroup PP
  */
 
 #endif  // PPAPI_C_PP_INPUT_EVENT_H_