Fill in PlatformPrivateFootprint on Linux 2/2

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 7db23920f1e1f560bb16e0760d4cbfe96f385332..696c58c8ae0d1c07bc3a7512eff69adcdaf9d65f 100644
--- a/components/tracing/common/process_metrics_memory_dump_provider.cc
+++ b/components/tracing/common/process_metrics_memory_dump_provider.cc
@@ -655,8 +655,8 @@ bool ProcessMetricsMemoryDumpProvider::DumpProcessTotals(
   if (!success)
     return false;
 
-  // TODO(hjd): Implement swap in the next CL.
   footprint.rss_anon_bytes = (resident_pages - shared_pages) * page_size;
+  footprint.vm_swap_bytes = process_metrics_->GetVmSwapBytes();
 #endif  // defined(OS_LINUX) || defined(OS_ANDROID)
 
 #if !defined(OS_IOS)