Upstream MemoryUma and use it for all activities.

chrome/android/java/src/org/chromium/chrome/browser/metrics/MemoryUma.java

Index: chrome/android/java/src/org/chromium/chrome/browser/metrics/MemoryUma.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/metrics/MemoryUma.java b/chrome/android/java/src/org/chromium/chrome/browser/metrics/MemoryUma.java
new file mode 100644
index 0000000000000000000000000000000000000000..5deefaad670f520f85fef7460fce17b3459ac6c9
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/metrics/MemoryUma.java
@@ -0,0 +1,89 @@
+// Copyright 2015 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.
+
+package org.chromium.chrome.browser.metrics;
+
+import static android.content.ComponentCallbacks2.TRIM_MEMORY_BACKGROUND;
+import static android.content.ComponentCallbacks2.TRIM_MEMORY_COMPLETE;
+import static android.content.ComponentCallbacks2.TRIM_MEMORY_MODERATE;
+import static android.content.ComponentCallbacks2.TRIM_MEMORY_RUNNING_CRITICAL;
+import static android.content.ComponentCallbacks2.TRIM_MEMORY_RUNNING_LOW;
+import static android.content.ComponentCallbacks2.TRIM_MEMORY_RUNNING_MODERATE;
+import static android.content.ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN;
+
+import android.os.Build;
+import android.os.SystemClock;
+
+import org.chromium.base.metrics.RecordHistogram;
+
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Centralizes UMA data collection for Android-specific memory conditions.
+ */
+public class MemoryUma {
+    // AndroidMemoryNotificationBackground defined in tools/metrics/histograms/histograms.xml.
+    private static final int BACKGROUND_TRIM_UI_HIDDEN = 0;
+    private static final int BACKGROUND_TRIM_BACKGROUND = 1;
+    private static final int BACKGROUND_TRIM_MODERATE = 2;
+    private static final int BACKGROUND_TRIM_COMPLETE = 3;
+    private static final int BACKGROUND_MAX = 4;
+
+    // AndroidMemoryNotificationForeground defined in tools/metrics/histograms/histograms.xml.
+    private static final int FOREGROUND_TRIM_MODERATE = 0;
+    private static final int FOREGROUND_TRIM_LOW = 1;
+    private static final int FOREGROUND_TRIM_CRITICAL = 2;
+    private static final int FOREGROUND_LOW = 3;
+    private static final int FOREGROUND_MAX = 4;
+
+    // Timestamp of the last time we received a LowMemory call since Chrome is in foreground.
+    private long mLastLowMemoryMsec = -1;
+
+    public void onStop() {
+        mLastLowMemoryMsec = -1;
+    }
+
+    public void onLowMemory() {
+        memoryNotificationForeground(FOREGROUND_LOW);
+        long now = SystemClock.elapsedRealtime();
+        if (mLastLowMemoryMsec >= 0) {
+            RecordHistogram.recordCustomTimesHistogram("MemoryAndroid.LowMemoryTimeBetween",
+                    now - mLastLowMemoryMsec, 0, TimeUnit.MINUTES.toMillis(10),
+                    TimeUnit.MILLISECONDS, 50);
+        }
+        mLastLowMemoryMsec = now;
+    }
+
+    public void onTrimMemory(int level) {
+        if (level >= TRIM_MEMORY_COMPLETE) {
+            memoryNotificationBackground(BACKGROUND_TRIM_COMPLETE);
+        } else if (level >= TRIM_MEMORY_MODERATE) {
+            memoryNotificationBackground(BACKGROUND_TRIM_MODERATE);
+        } else if (level >= TRIM_MEMORY_BACKGROUND) {
+            memoryNotificationBackground(BACKGROUND_TRIM_BACKGROUND);
+        } else if (level >= TRIM_MEMORY_UI_HIDDEN) {
+            memoryNotificationBackground(BACKGROUND_TRIM_UI_HIDDEN);
+        } else if (level >= TRIM_MEMORY_RUNNING_CRITICAL) {
+            memoryNotificationForeground(FOREGROUND_TRIM_CRITICAL);
+        } else if (level >= TRIM_MEMORY_RUNNING_LOW) {
+            memoryNotificationForeground(FOREGROUND_TRIM_LOW);
+        } else if (level >= TRIM_MEMORY_RUNNING_MODERATE) {
+            memoryNotificationForeground(FOREGROUND_TRIM_MODERATE);
+        }
+    }
+
+    private static void memoryNotificationForeground(int notification) {
+        assert notification >= 0 && notification < FOREGROUND_MAX;
+        // Before Jelly Bean we have only LowMemory foreground notification.
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN) return;
+        RecordHistogram.recordEnumeratedHistogram("MemoryAndroid.NotificationForeground",
+                notification, FOREGROUND_MAX);
+    }
+
+    private static void memoryNotificationBackground(int notification) {
+        assert notification >= 0 && notification < BACKGROUND_MAX;
+        RecordHistogram.recordEnumeratedHistogram("MemoryAndroid.NotificationBackground",
+                notification, BACKGROUND_MAX);
+    }
+}