Expose Delete Storage API

Expose a function through Storage to allow developers to delete the
database that backs storage.

Issue #1230
Issue #1248

Change-Id: Icb20b6c43966a299d8903b2d14f33666f672bd15

lib/offline/storage.js

@@ -1087,4 +1087,15 @@ shaka.offline.Storage.getAllSegmentIds_ = function(manifest) {
 };
 
 
+/**
+ * Delete the on-disk storage and all content it contains. This should not
+ * be done regularly, only when storage is rendered unusable.
+ * @return {!Promise}
+ */
+shaka.offline.Storage.deleteAll = function() {
+  return shaka.offline.StorageEngineFactory.deleteStorage();
+};
+
+
+
 shaka.Player.registerSupportPlugin('offline', shaka.offline.Storage.support);

lib/offline/storage_engine_factory.js

@@ -27,6 +27,12 @@ goog.require('shaka.util.Error');
  */
 
 
+/**
+ * @const{string}
+ * @private
+ */
+shaka.offline.StorageEngineFactory.NAME_ = 'shaka_offline_db';
+
 /**
  * Determines if this platform supports any form of storage engine.
  * @return {boolean}
@@ -42,17 +48,40 @@ shaka.offline.StorageEngineFactory.isSupported = function() {
  * @return {!Promise<!shaka.offline.IStorageEngine>}
  */
 shaka.offline.StorageEngineFactory.createStorageEngine = function() {
+  const name = shaka.offline.StorageEngineFactory.NAME_;
+
+  return shaka.offline.StorageEngineFactory.ensureSupport().then(() => {
+    let engine = new shaka.offline.DBEngine(name);
+    return engine.init().then(() => engine);
+  });
+};
+
+
+/**
+ * Delete the storage engine and all its contents. This operation is
+ * non-reversible.
+ * @return {!Promise}
+ */
+shaka.offline.StorageEngineFactory.deleteStorage = function() {
+  const name = shaka.offline.StorageEngineFactory.NAME_;
+
+  return shaka.offline.StorageEngineFactory.ensureSupport().then(() => {
+    return shaka.offline.DBEngine.deleteDatabase(name);
+  });
+};
+
+
+/** @return {!Promise} */
+shaka.offline.StorageEngineFactory.ensureSupport = function() {
   // Use our method to check in case it was replaced.
-  var supportsStorage = shaka.offline.StorageEngineFactory.isSupported();
+  let support = shaka.offline.StorageEngineFactory.isSupported();
 
-  if (!supportsStorage) {
+  if (support) {
+    return Promise.resolve();
+  } else {
     return Promise.reject(new shaka.util.Error(
         shaka.util.Error.Severity.CRITICAL,
         shaka.util.Error.Category.STORAGE,
         shaka.util.Error.Code.STORAGE_NOT_SUPPORTED));
   }
-
-  /** @type {!shaka.offline.DBEngine} */
-  var engine = new shaka.offline.DBEngine('shaka_offline_db');
-  return engine.init().then(function() { return engine; });
 };