Add a histogram for total private memory footprint.

chrome/browser/metrics/process_memory_metrics_emitter.cc

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/metrics/process_memory_metrics_emitter.h"
 
 #include "base/metrics/histogram_macros.h"
 #include "base/trace_event/memory_dump_request_args.h"
 #include "content/public/common/service_manager_connection.h"
 #include "content/public/common/service_names.mojom.h"
@@ skipping 65 matching lines @@
 
 void ProcessMemoryMetricsEmitter::ReceivedMemoryDump(
     uint64_t dump_guid,
     bool success,
     memory_instrumentation::mojom::GlobalMemoryDumpPtr ptr) {
   if (!success)
     return;
   if (!ptr)
     return;
 
+  uint32_t private_footprint_total_kb = 0;
   for (const ProcessMemoryDumpPtr& pmd : ptr->process_dumps) {
+    private_footprint_total_kb += pmd->private_footprint;
     switch (pmd->process_type) {
       case memory_instrumentation::mojom::ProcessType::BROWSER:
         EmitBrowserMemoryMetrics(pmd);
         break;
       case memory_instrumentation::mojom::ProcessType::RENDERER:
         EmitRendererMemoryMetrics(pmd);
         break;
       case memory_instrumentation::mojom::ProcessType::GPU:
         EmitGpuMemoryMetrics(pmd);
         break;
       case memory_instrumentation::mojom::ProcessType::UTILITY:
       case memory_instrumentation::mojom::ProcessType::PLUGIN:
       case memory_instrumentation::mojom::ProcessType::OTHER:
         break;
     }
   }
+  UMA_HISTOGRAM_MEMORY_LARGE_MB(
+      "Memory.Experimental.Total2.PrivateMemoryFootprint",
+      private_footprint_total_kb / 1024);
 }