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

Also add a few checked_cast for places where we converted from size_t and we're sure that it's safe.

BUG=581409

Review URL: https://codereview.chromium.org/1684793003

Cr-Commit-Position: refs/heads/master@{#374788}

2 files changed, 5 insertions, 3 deletions

diff --git a/content/common/gpu/gpu_memory_manager.cc b/content/common/gpu/gpu_memory_manager.cc
index 4b9eb7c..10f769c 100644
--- a/content/common/gpu/gpu_memory_manager.cc
+++ b/content/common/gpu/gpu_memory_manager.cc
@@ -118,7 +118,7 @@ void GpuMemoryManager::SendUmaStatsToBrowser() {
   GPUMemoryUmaStats params;
   params.bytes_allocated_current = GetCurrentUsage();
   params.bytes_allocated_max = bytes_allocated_historical_max_;
-  params.context_group_count = tracking_groups_.size();
+  params.context_group_count = static_cast<uint32_t>(tracking_groups_.size());
   channel_manager_->Send(new GpuHostMsg_GpuMemoryUmaStats(params));
 }
 }  // namespace content
diff --git a/content/common/gpu/gpu_memory_uma_stats.h b/content/common/gpu/gpu_memory_uma_stats.h
index 16c8813..daf91bf 100644
--- a/content/common/gpu/gpu_memory_uma_stats.h
+++ b/content/common/gpu/gpu_memory_uma_stats.h
@@ -11,6 +11,8 @@ namespace content {
 
 // Memory usage statistics send periodically to the browser process to report
 // in UMA histograms if the GPU process crashes.
+// 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 GPUMemoryUmaStats {
   GPUMemoryUmaStats()
       : bytes_allocated_current(0),
@@ -19,10 +21,10 @@ struct GPUMemoryUmaStats {
   }
 
   // The number of bytes currently allocated.
-  uint32_t bytes_allocated_current;
+  uint64_t bytes_allocated_current;
 
   // The maximum number of bytes ever allocated at once.
-  uint32_t bytes_allocated_max;
+  uint64_t bytes_allocated_max;
 
   // The number of context groups.
   uint32_t context_group_count;