Add comments for struct members that were changed from size_t to uin32_t or uint64_t for IPC safety.

media/cast/logging/logging_defines.h

 // Copyright 2013 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 MEDIA_CAST_LOGGING_LOGGING_DEFINES_H_
 #define MEDIA_CAST_LOGGING_LOGGING_DEFINES_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 46 matching lines @@
   ~FrameEvent();
 
   RtpTimeTicks rtp_timestamp;
   uint32_t frame_id;
 
   // Resolution of the frame. Only set for video FRAME_CAPTURE_END events.
   int width;
   int height;
 
   // Size of encoded frame in bytes. Only set for FRAME_ENCODED event.
+  // Note: we use uint32_t instead of size_t for byte count because this struct
+  // is sent over IPC which could span 32 & 64 bit processes.
   uint32_t size;
 
   // Time of event logged.
   base::TimeTicks timestamp;
 
   CastLoggingEvent type;
 
   EventMediaType media_type;
 
   // Only set for FRAME_PLAYOUT events.
@@ skipping 28 matching lines @@
   // Time of event logged.
   base::TimeTicks timestamp;
   CastLoggingEvent type;
   EventMediaType media_type;
 };
 
 }  // namespace cast
 }  // namespace media
 
 #endif  // MEDIA_CAST_LOGGING_LOGGING_DEFINES_H_