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

Index: content/public/common/gpu_memory_stats.h
diff --git a/content/public/common/gpu_memory_stats.h b/content/public/common/gpu_memory_stats.h
index 09bda3fe52b9b9a7dd387d42719c60645efe0354..5a6337bc488f9523216037007e2a00a906d8b441 100644
--- a/content/public/common/gpu_memory_stats.h
+++ b/content/public/common/gpu_memory_stats.h
@@ -17,6 +17,8 @@
 
 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();
@@ -26,7 +28,7 @@ struct CONTENT_EXPORT GPUVideoMemoryUsageStats {
     ~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
@@ -39,10 +41,10 @@ struct CONTENT_EXPORT GPUVideoMemoryUsageStats {
   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