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

content/public/common/gpu_memory_stats.h

 // Copyright (c) 2012 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 CONTENT_PUBLIC_COMMON_GPU_MEMORY_STATS_H_
 #define CONTENT_PUBLIC_COMMON_GPU_MEMORY_STATS_H_
 
 // Provides access to the GPU information for the system
 // on which chrome is currently running.
 
 #include <stddef.h>
 
 #include <map>
 
 #include "base/process/process.h"
 #include "content/common/content_export.h"
 
 namespace content {
 
+// Note: we use uint64_t instead of size_t for byte count because this struct
+// is sent over IPC which could span 32 & 64 bit processes.
 struct CONTENT_EXPORT GPUVideoMemoryUsageStats {
   GPUVideoMemoryUsageStats();
   ~GPUVideoMemoryUsageStats();
 
   struct CONTENT_EXPORT ProcessStats {
     ProcessStats();
     ~ProcessStats();
 
     // The bytes of GPU resources accessible by this process
-    uint32_t video_memory;
+    uint64_t video_memory;
 
     // Set to true if this process' GPU resource count is inflated because
     // it is counting other processes' resources (e.g, the GPU process has
     // duplicate set to true because it is the aggregate of all processes)
     bool has_duplicates;
   };
   typedef std::map<base::ProcessId, ProcessStats> ProcessMap;
 
   // A map of processes to their GPU resource consumption
   ProcessMap process_map;
 
   // The total amount of GPU memory allocated at the time of the request.
-  uint32_t bytes_allocated;
+  uint64_t bytes_allocated;
 
   // The maximum amount of GPU memory ever allocated at once.
-  uint32_t bytes_allocated_historical_max;
+  uint64_t bytes_allocated_historical_max;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_COMMON_GPU_MEMORY_STATS_H_