Revert of [Android Refactor] Merge WebappDataStorage#LAST_USED_UNSET and LAST_USED_INVALID

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 ecba3522f26ecb8349a1665177d1461d8cc88110..c8b2e8ddc10a190f4aa2b84d92012d6f199e749b 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
@@ -84,9 +84,10 @@
     // The default shell Apk version of WebAPKs.
     static final int DEFAULT_SHELL_APK_VERSION = 1;
 
-    // Invalid constants for timestamps and URLs. '0' is used as the invalid timestamp as
-    // WebappRegistry and WebApkUpdateManager assume that timestamps are always valid.
-    static final long TIMESTAMP_INVALID = 0;
+    // Unset/invalid constants for last used times and URLs. 0 is used as the null last used time as
+    // WebappRegistry assumes that this is always a valid timestamp.
+    static final long LAST_USED_UNSET = 0;
+    static final long LAST_USED_INVALID = -1;
     static final String URL_INVALID = "";
     static final int VERSION_INVALID = 0;
 
@@ -138,8 +139,14 @@
      * Opens an instance of WebappDataStorage for the web app specified.
      * @param webappId The ID of the web app.
      */
-    static WebappDataStorage open(String webappId) {
-        return sFactory.create(webappId);
+    static WebappDataStorage open(final String webappId) {
+        final WebappDataStorage storage = sFactory.create(webappId);
+        if (storage.getLastUsedTime() == LAST_USED_INVALID) {
+            // If the last used time is invalid then ensure that there is no data in the
+            // WebappDataStorage which needs to be cleaned up.
+            assert storage.isEmpty();
+        }
+        return storage;
     }
 
     /**
@@ -314,7 +321,10 @@
     void clearHistory() {
         SharedPreferences.Editor editor = mPreferences.edit();
 
-        editor.remove(KEY_LAST_USED);
+        // The last used time is set to 0 to ensure that a valid value is always present.
+        // 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_URL);
         editor.remove(KEY_SCOPE);
         editor.remove(KEY_LAST_CHECK_WEB_MANIFEST_UPDATE_TIME);
@@ -354,7 +364,7 @@
      * Returns the last used time of this object, or -1 if it is not stored.
      */
     public long getLastUsedTime() {
-        return mPreferences.getLong(KEY_LAST_USED, TIMESTAMP_INVALID);
+        return mPreferences.getLong(KEY_LAST_USED, LAST_USED_INVALID);
     }
 
     /**
@@ -396,7 +406,7 @@
      * updated. This time needs to be set when the WebAPK is registered.
      */
     private long getLastCheckForWebManifestUpdateTime() {
-        return mPreferences.getLong(KEY_LAST_CHECK_WEB_MANIFEST_UPDATE_TIME, TIMESTAMP_INVALID);
+        return mPreferences.getLong(KEY_LAST_CHECK_WEB_MANIFEST_UPDATE_TIME, LAST_USED_INVALID);
     }
 
     /**
@@ -413,7 +423,7 @@
      * This time needs to be set when the WebAPK is registered.
      */
     long getLastWebApkUpdateRequestCompletionTime() {
-        return mPreferences.getLong(KEY_LAST_UPDATE_REQUEST_COMPLETE_TIME, TIMESTAMP_INVALID);
+        return mPreferences.getLong(KEY_LAST_UPDATE_REQUEST_COMPLETE_TIME, LAST_USED_INVALID);
     }
 
     /**
@@ -475,7 +485,7 @@
      */
     boolean didPreviousUpdateSucceed() {
         long lastUpdateCompletionTime = getLastWebApkUpdateRequestCompletionTime();
-        if (lastUpdateCompletionTime == TIMESTAMP_INVALID) {
+        if (lastUpdateCompletionTime == WebappDataStorage.LAST_USED_INVALID) {
             return true;
         }
         return getDidLastWebApkUpdateRequestSucceed();