tracing: Add private footprint

tracing/tracing/metrics/system_health/memory_metric.html

Index: tracing/tracing/metrics/system_health/memory_metric.html
diff --git a/tracing/tracing/metrics/system_health/memory_metric.html b/tracing/tracing/metrics/system_health/memory_metric.html
index 3000abbdb5770d4121e7961319805438368ce6cf..2e4777061e56977099b6021e8f8b97e02c0dc73e 100644
--- a/tracing/tracing/metrics/system_health/memory_metric.html
+++ b/tracing/tracing/metrics/system_health/memory_metric.html
@@ -257,6 +257,12 @@ tr.exportTo('tr.metrics.sh', function() {
               component: ['system_memory'],
               value: processDump.totals.peakResidentBytes
             });
+            addProcessScalar({
+              source: 'reported_by_os',
+              property: PRIVATE_FOOTPRINT_SIZE,
+              component: ['system_memory'],
+              value: processDump.totals.privateFootprintBytes,
+            });
           }
 
           // Add memory:<browser-name>:<process-name>:reported_by_chrome:...
@@ -560,6 +566,15 @@ tr.exportTo('tr.metrics.sh', function() {
     }
   };
 
+  const PRIVATE_FOOTPRINT_SIZE = {
+    name: 'private_footprint_size',
+    unit: sizeInBytes_smallerIsBetter,
+    buildDescriptionPrefix(componentPath, processName) {
+      return buildOsValueDescriptionPrefix(componentPath, processName,
+          'private footprint size');
+    }
+  };
+
   /**
    * Build a description prefix for a memory:<browser-name>:<process-name>:
    * reported_by_os:... value.