Add a histogram for total private memory footprint.

Also update tests to check for private memory footprint on Windows, which is now
implemented.

BUG=

Review-Url: https://codereview.chromium.org/2904703002
Cr-Commit-Position: refs/heads/master@{#474931}

chrome/browser/metrics/process_memory_metrics_emitter.cc

@@ -83,7 +83,9 @@ void ProcessMemoryMetricsEmitter::ReceivedMemoryDump(
   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);
@@ -100,4 +102,7 @@ void ProcessMemoryMetricsEmitter::ReceivedMemoryDump(
         break;
     }
   }
+  UMA_HISTOGRAM_MEMORY_LARGE_MB(
+      "Memory.Experimental.Total2.PrivateMemoryFootprint",
+      private_footprint_total_kb / 1024);
 }

chrome/browser/metrics/process_memory_metrics_emitter_browsertest.cc

@@ -86,19 +86,12 @@ void CheckMemoryMetric(const std::string& name,
 
 void CheckAllMemoryMetrics(const base::HistogramTester& histogram_tester,
                            int count) {
-#if (defined(OS_MACOSX) && !defined(OS_IOS)) || defined(OS_LINUX) || \
-    defined(OS_ANDROID)
-  bool private_footprint_implemented = true;
-#else
-  bool private_footprint_implemented = false;
-#endif
-
   CheckMemoryMetric("Memory.Experimental.Browser2.Malloc", histogram_tester,
                     count, true);
   CheckMemoryMetric("Memory.Experimental.Browser2.Resident", histogram_tester,
                     count, true);
   CheckMemoryMetric("Memory.Experimental.Browser2.PrivateMemoryFootprint",
-                    histogram_tester, count, private_footprint_implemented);
+                    histogram_tester, count, true);
   CheckMemoryMetric("Memory.Experimental.Renderer2.Malloc", histogram_tester,
                     count, true);
   CheckMemoryMetric("Memory.Experimental.Renderer2.Resident", histogram_tester,
@@ -110,7 +103,9 @@ void CheckAllMemoryMetrics(const base::HistogramTester& histogram_tester,
   CheckMemoryMetric("Memory.Experimental.Renderer2.V8", histogram_tester, count,
                     true);
   CheckMemoryMetric("Memory.Experimental.Renderer2.PrivateMemoryFootprint",
-                    histogram_tester, count, private_footprint_implemented);
+                    histogram_tester, count, true);
+  CheckMemoryMetric("Memory.Experimental.Total2.PrivateMemoryFootprint",
+                    histogram_tester, count, true);
 }
 
 }  // namespace

tools/metrics/histograms/histograms.xml

@@ -30455,6 +30455,13 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Memory.Experimental.Total2.PrivateMemoryFootprint" units="MB">
+  <owner>erikchen@chromium.org</owner>
+  <summary>
+    A rough estimate of the private memory footprint of all processes.
+  </summary>
+</histogram>
+
 <histogram name="Memory.Extension" units="KB">
   <owner>hajimehoshi@chromium.org</owner>
   <owner>kenjibaheux@google.com</owner>