mac: Fix calulation for number of resident pages in a process.

chrome/browser/task_manager/sampling/task_group_sampler.cc

Index: chrome/browser/task_manager/sampling/task_group_sampler.cc
diff --git a/chrome/browser/task_manager/sampling/task_group_sampler.cc b/chrome/browser/task_manager/sampling/task_group_sampler.cc
index 9cf7872049e0c03b79a91670b51dbab995f02a59..c9b8877a4b1413d99fbdfbfc2df99f164a10ac70 100644
--- a/chrome/browser/task_manager/sampling/task_group_sampler.cc
+++ b/chrome/browser/task_manager/sampling/task_group_sampler.cc
@@ -126,14 +126,13 @@ MemoryUsageStats TaskGroupSampler::RefreshMemoryUsage() {
 
   MemoryUsageStats memory_usage;
 #if defined(OS_MACOSX)
-  memory_usage.physical_bytes =

[Mark Mentovai, 2017/03/13 18:13:33]

Leaving this alone was nice because it consolidates all of our “what is working
set size?” logic in the Mac implementation file.

[ssid, 2017/03/13 18:44:55]

Yes, the main consumer of this number I'd expect would be the users and IIUC
they'd see different number in Chrome task manager and system task manager.

[Mark Mentovai, 2017/03/13 18:48:03]

ssid wrote:
What I meant was “use the new logic, just consolidate it.” Are you suggesting
“use the old logic” for one or more use sites?

[ssid, 2017/03/13 18:59:14]

Um sorry, yes I just felt showing different number in Chrome task manager and
system's might be get bad? It's just an opinion, I am fine with the change.

[erikchen, 2017/03/13 21:00:41]

Calculating private/shared bytes has a performance cost [order of magnitude:
1ms]. Keeping the existing API would require running that calculation twice.
I'll add a new macOS-only function to base/process/process_metrics.h that
returns private bytes, shared privates, and working set size.

-      static_cast<int64_t>(process_metrics_->GetWorkingSetSize());
-
   size_t private_bytes = 0;
   size_t shared_bytes = 0;
   if (process_metrics_->GetMemoryBytes(&private_bytes, &shared_bytes)) {
     memory_usage.private_bytes = static_cast<int64_t>(private_bytes);
     memory_usage.shared_bytes = static_cast<int64_t>(shared_bytes);
+    memory_usage.physical_bytes =
+        memory_usage.private_bytes + memory_usage.shared_bytes;
   }
 #else
   // Refreshing the physical/private/shared memory at one shot.