Add UMA metric to track the time elapsed since a WebAPK was last launched

base/android/java/src/org/chromium/base/metrics/RecordHistogram.java

Index: base/android/java/src/org/chromium/base/metrics/RecordHistogram.java
diff --git a/base/android/java/src/org/chromium/base/metrics/RecordHistogram.java b/base/android/java/src/org/chromium/base/metrics/RecordHistogram.java
index eaf57b7ce7b346c90a4ecbe4e67ab5358872a17a..b3667c5515312374d9e8c4fbf1008edb8ed10985 100644
--- a/base/android/java/src/org/chromium/base/metrics/RecordHistogram.java
+++ b/base/android/java/src/org/chromium/base/metrics/RecordHistogram.java
@@ -269,6 +269,15 @@ public class RecordHistogram {
         return nativeGetHistogramValueCountForTesting(name, sample);
     }
 
+    /**
+     * Returns the number of samples recorded for the given histogram.
+     * @param name name of the histogram to look up.
+     */
+    @VisibleForTesting
+    public static int getHistogramTotalCountForTesting(String name) {
+        return nativeGetHistogramTotalCountForTesting(name);
+    }
+
     /**
      * Initializes the metrics system.
      */
@@ -290,5 +299,6 @@ public class RecordHistogram {
     private static native long nativeRecordSparseHistogram(String name, long key, int sample);
 
     private static native int nativeGetHistogramValueCountForTesting(String name, int sample);
+    private static native int nativeGetHistogramTotalCountForTesting(String name);
     private static native void nativeInitialize();
 }