Add a field platform_private_footprint_ to ProcessMemoryTotals.

components/tracing/common/process_metrics_memory_dump_provider.cc

Index: components/tracing/common/process_metrics_memory_dump_provider.cc
diff --git a/components/tracing/common/process_metrics_memory_dump_provider.cc b/components/tracing/common/process_metrics_memory_dump_provider.cc
index a9fe6b5aa74e9083309eb3d3adb74a07a51c90b3..37b9656e00928be9af97d45eec98aa297fe76f2d 100644
--- a/components/tracing/common/process_metrics_memory_dump_provider.cc
+++ b/components/tracing/common/process_metrics_memory_dump_provider.cc
@@ -622,6 +622,14 @@ bool ProcessMetricsMemoryDumpProvider::DumpProcessTotals(
   pmd->process_totals()->SetExtraFieldInBytes("private_bytes", private_bytes);
   pmd->process_totals()->SetExtraFieldInBytes("shared_bytes", shared_bytes);
   pmd->process_totals()->SetExtraFieldInBytes("locked_bytes", locked_bytes);
+
+  if (mac::IsAtLeastOS10_12()) {
+    pmd->process_totals()->set_private_footprint_precursor(
+        process_metrics_->GetPhysicalFootprint());
+  } else {
+    pmd->process_totals()->set_private_footprint_precursor(
+        process_metrics_->GetInternalAndCompressed());
+  }
 #else
   uint64_t rss_bytes = process_metrics_->GetWorkingSetSize();
 #endif  // defined(OS_MACOSX)