memory coordinator: Add metrics for Android's onTrimMemory()

content/browser/memory/memory_monitor_android.cc

Index: content/browser/memory/memory_monitor_android.cc
diff --git a/content/browser/memory/memory_monitor_android.cc b/content/browser/memory/memory_monitor_android.cc
index 70c1e6dc4ca377cd3080b8545f38a1427a2b184b..ba73f7363bf5f30b91d711892f0381dc89c4f0b1 100644
--- a/content/browser/memory/memory_monitor_android.cc
+++ b/content/browser/memory/memory_monitor_android.cc
@@ -7,12 +7,22 @@
 #include "base/android/context_utils.h"
 #include "base/android/jni_android.h"
 #include "base/memory/ptr_util.h"
+#include "base/metrics/histogram_macros.h"
+#include "content/browser/memory/memory_coordinator.h"
 #include "jni/MemoryMonitorAndroid_jni.h"
 
 namespace content {
 
 namespace {
+
 const size_t kMBShift = 20;
+
+void RegisterComponentCallbacks() {
+  Java_MemoryMonitorAndroid_registerComponentCallbacks(
+      base::android::AttachCurrentThread(),
+      base::android::GetApplicationContext());
+}
+
 }
 
 // An implementation of MemoryMonitorAndroid::Delegate using the Android APIs.
@@ -54,6 +64,34 @@ static void GetMemoryInfoCallback(
   info->total_mem = total_mem;
 }
 
+// The maximum level of onTrimMemory (TRIM_MEMORY_COMPLETE).
+const int kTrimMemoryLevelMax = 0x80;
+
+// Called by JNI.
+static void OnTrimMemory(JNIEnv* env,
+                         const base::android::JavaParamRef<jclass>& jcaller,
+                         jint level) {
+  DCHECK(level >= 0 && level <= kTrimMemoryLevelMax);
+  auto state = MemoryCoordinator::GetInstance()->GetCurrentMemoryState();
+  switch (state) {
+    case base::MemoryState::NORMAL:
+      UMA_HISTOGRAM_ENUMERATION("Memory.Coordinator.TrimMemoryLevel.Normal",
+                                level, kTrimMemoryLevelMax);
+      break;
+    case base::MemoryState::THROTTLED:
+      UMA_HISTOGRAM_ENUMERATION("Memory.Coordinator.TrimMemoryLevel.Throttled",
+                                level, kTrimMemoryLevelMax);
+      break;
+    case base::MemoryState::SUSPENDED:
+      UMA_HISTOGRAM_ENUMERATION("Memory.Coordinator.TrimMemoryLevel.Suspended",
+                                level, kTrimMemoryLevelMax);
+      break;
+    case base::MemoryState::UNKNOWN:
+      NOTREACHED();
+      break;
+  }
+}
+
 // static
 std::unique_ptr<MemoryMonitorAndroid> MemoryMonitorAndroid::Create() {
   auto delegate = base::WrapUnique(new MemoryMonitorAndroidDelegateImpl);
@@ -68,6 +106,7 @@ bool MemoryMonitorAndroid::Register(JNIEnv* env) {
 MemoryMonitorAndroid::MemoryMonitorAndroid(std::unique_ptr<Delegate> delegate)
     : delegate_(std::move(delegate)) {
   DCHECK(delegate_.get());
+  RegisterComponentCallbacks();
 }
 
 MemoryMonitorAndroid::~MemoryMonitorAndroid() {}