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

chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappDataStorage.java

Index: chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappDataStorage.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappDataStorage.java b/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappDataStorage.java
index c8b2e8ddc10a190f4aa2b84d92012d6f199e749b..fdf9c5669f497f9786d298035d2c1d308223021c 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappDataStorage.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappDataStorage.java
@@ -33,6 +33,7 @@ public class WebappDataStorage {
     static final String SHARED_PREFS_FILE_PREFIX = "webapp_";
     static final String KEY_SPLASH_ICON = "splash_icon";
     static final String KEY_LAST_USED = "last_used";
+    static final String KEY_WAS_LAUNCHED = "was_launched";

[dominickn, 2017/06/08 05:15:27]

I'd call this "HAS_BEEN_LAUNCHED"

     static final String KEY_URL = "url";
     static final String KEY_SCOPE = "scope";
     static final String KEY_ICON = "icon";
@@ -301,7 +302,13 @@ public class WebappDataStorage {
      * Returns true if this web app has been launched from home screen recently (within
      * WEBAPP_LAST_OPEN_MAX_TIME milliseconds).
      */
-    public boolean wasLaunchedRecently() {
+    /**

[Xi Han, 2017/06/09 14:55:35]

Please merge the comments above with the ones below.

+     * Returns true if this web app recently (within WEBAPP_LAST_OPEN_MAX_TIME milliseconds) was
+     * either:
+     * - registered with WebappRegistry
+     * - launched from the homescreen
+     */
+    public boolean wasUsedRecently() {

[dominickn, 2017/06/08 05:15:27]

I'd prefer that this method kept the same name. The additional comment really
isn't necessary because all of that information is already present (you could if
you wanted to move the comment within the method up to the Javadoc above).

[pkotwicz, 2017/06/12 20:34:46]

I think that having *used* in the name of the function makes sense given that
this function checks last_used and the timestamp is updated via
updateLastUsedTime()

I have merged the two comments together

         // WebappRegistry.register sets the last used time, so that counts as a 'launch'.
         return (sClock.currentTimeMillis() - getLastUsedTime() < WEBAPP_LAST_OPEN_MAX_TIME);
     }
@@ -325,6 +332,7 @@ public class WebappDataStorage {
         // If the web app is not launched prior to the next cleanup, then its remaining data will be
         // removed. Otherwise, the next launch from home screen will update the last used time.
         editor.putLong(KEY_LAST_USED, LAST_USED_UNSET);
+        editor.remove(KEY_WAS_LAUNCHED);
         editor.remove(KEY_URL);
         editor.remove(KEY_SCOPE);
         editor.remove(KEY_LAST_CHECK_WEB_MANIFEST_UPDATE_TIME);
@@ -384,6 +392,16 @@ public class WebappDataStorage {
         mPreferences.edit().putLong(KEY_LAST_USED, sClock.currentTimeMillis()).apply();
     }
 
+    /** Returns whether the web app was launched from the home screen. */
+    boolean wasLaunched() {

[dominickn, 2017/06/08 05:15:27]

Call this "hasBeenLaunched()", and update the comment to say "Returns true if
the web app has been launched at least once from the home screen".

+        return mPreferences.getBoolean(KEY_WAS_LAUNCHED, false);
+    }
+
+    /** Sets the web app as having been launched from the home screen. */
+    void setWasLaunched() {

[dominickn, 2017/06/08 05:15:27]

setHasBeenLaunched(). Ditto with the comment.

+        mPreferences.edit().putBoolean(KEY_WAS_LAUNCHED, true).apply();
+    }
+
     /**
      * Returns the package name if the data is for a WebAPK, null otherwise.
      */