[Android] Support startup histogram.

chrome/android/java/src/org/chromium/chrome/browser/UmaUtils.java

Index: chrome/android/java/src/org/chromium/chrome/browser/UmaUtils.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/UmaUtils.java b/chrome/android/java/src/org/chromium/chrome/browser/UmaUtils.java
new file mode 100644
index 0000000000000000000000000000000000000000..deb568ae5cfc44657157139db258fdffd929ec8e
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/UmaUtils.java
@@ -0,0 +1,33 @@
+// Copyright 2013 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;
+
+import org.chromium.base.CalledByNative;
+
+/**
+ * Utilities to support startup metrics - Android version.
+ */
+public class UmaUtils {
+
+    private static long sApplicationStartWallClockMs;
+
+    /**
+     * Record the time at which the activity started. This should be called asap after
+     * the start of the activity's onCreate function.
+     */
+    public static void recordMainEntryPointTime() {
+        // We can't simply pass this down through a JNI call, since the JNI for chrome
+        // isn't initialized until we start the native content browser component, and we
+        // then need the start time in the C++ side before we return to Java. As such we
+        // save it in a static that the C++ can fetch once it has initialized the JNI.
+        sApplicationStartWallClockMs = System.currentTimeMillis();
+    }
+
+    @CalledByNative
+    private static long getMainEntryPointTime() {
+        return sApplicationStartWallClockMs;
+    }
+
+}