Add StateOn{Moderate,Critical}NotificationReceived metrics

content/browser/memory/memory_coordinator.cc

Index: content/browser/memory/memory_coordinator.cc
diff --git a/content/browser/memory/memory_coordinator.cc b/content/browser/memory/memory_coordinator.cc
index 517aaedc34a1a13f696d9e0532c5c4c9117458a1..513d9177d5971911a0241cee364cf9942520370f 100644
--- a/content/browser/memory/memory_coordinator.cc
+++ b/content/browser/memory/memory_coordinator.cc
@@ -5,6 +5,7 @@
 #include "content/browser/memory/memory_coordinator.h"
 
 #include "base/memory/memory_coordinator_client_registry.h"
+#include "base/metrics/histogram_macros.h"
 #include "content/public/browser/content_browser_client.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/common/content_client.h"
@@ -120,6 +121,27 @@ mojom::MemoryState MemoryCoordinator::GetMemoryState(
   return iter->second.memory_state;
 }
 
+void MemoryCoordinator::RecordMemoryPressure(
+    base::MemoryPressureMonitor::MemoryPressureLevel level) {
+  int state = static_cast<int>(GetCurrentMemoryState());
+  switch (level) {
+    case base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_MODERATE:
+      UMA_HISTOGRAM_ENUMERATION(
+          "Memory.Coordinator.StateOnModerateNotificationReceived",
+          state, base::kMemoryStateMax);
+      break;
+    case base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL:
+      UMA_HISTOGRAM_ENUMERATION(
+          "Memory.Coordinator.StateOnCriticalNotificationReceived",
+          state, base::kMemoryStateMax);
+      break;
+    case base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE:
+      // Fall through
+    default:

[Ilya Sherman, 2016/11/07 19:28:52]

nit: It's generally best to omit the default case, and instead to list each
possible case explicitly.  That way, if a new enum constant is ever added, the
author will need to make a conscious decision for how to handle it here.

[bashi, 2016/11/08 00:33:35]

Done.

+      NOTREACHED();
+  }
+}
+
 void MemoryCoordinator::EnableFeaturesForTesting() {
   base::FeatureList::ClearInstanceForTesting();
   std::unique_ptr<base::FeatureList> feature_list(new base::FeatureList);