Set password sooner to avoid redundant persistance

The vault password is now always set in the method responsible for
creating the vault. Previously it was set when the vault was persisted,
or when the first keyring was created. This led to redundant calls to
persist the keyrings, just to achieve the side-effect of setting the
password.

This change eliminates those redundant calls, and a few more that had
no obvious purpose.

Note that the password is also set on unlock, and that has not changed
here.

Author: Gudahtt

index.js

@@ -78,8 +78,9 @@ class KeyringController extends EventEmitter {
    * @returns {Promise<Object>} A Promise that resolves to the state.
    */
   async createNewVaultAndKeychain(password) {
-    await this.createFirstKeyTree(password);
-    await this.persistAllKeyrings(password);
+    this.password = password;
+
+    await this.createFirstKeyTree();
     this.setUnlocked();
     this.fullUpdate();
   }
@@ -116,9 +117,9 @@ class KeyringController extends EventEmitter {
       throw new Error('Seed phrase is invalid.');
     }
 
-    this.clearKeyrings();
+    this.password = password;
 
-    await this.persistAllKeyrings(password);
+    this.clearKeyrings();
     const firstKeyring = await this.addNewKeyring(
       KEYRINGS_TYPE_MAP.HD_KEYRING,
       {
@@ -130,8 +131,6 @@ class KeyringController extends EventEmitter {
     if (!firstAccount) {
       throw new Error('KeyringController - First Account not found.');
     }
-
-    await this.persistAllKeyrings(password);
     this.setUnlocked();
     return this.fullUpdate();
   }
@@ -487,11 +486,9 @@ class KeyringController extends EventEmitter {
    * - Faucets that account on testnet
    * - Puts the current seed words into the state tree
    *
-   * @param {string} password - The keyring controller password.
    * @returns {Promise<void>} - A promise that resolves if the operation was successful.
    */
-  async createFirstKeyTree(password) {
-    this.password = password;
+  async createFirstKeyTree() {
     this.clearKeyrings();
 
     const keyring = await this.addNewKeyring(KEYRINGS_TYPE_MAP.HD_KEYRING);
@@ -513,15 +510,9 @@ class KeyringController extends EventEmitter {
    * encrypts that array with the provided `password`,
    * and persists that encrypted string to storage.
    *
-   * @param {string} password - The keyring controller password.
    * @returns {Promise<boolean>} Resolves to true once keyrings are persisted.
    */
-  async persistAllKeyrings(password = this.password) {
-    if (typeof password !== 'string') {
-      throw new Error('KeyringController - password is not a string');
-    }
-
-    this.password = password;
+  async persistAllKeyrings() {
     const serializedKeyrings = await Promise.all(
       this.keyrings.map(async (keyring) => {
         const [type, data] = await Promise.all([
@@ -752,7 +743,7 @@ class KeyringController extends EventEmitter {
   forgetKeyring(keyring) {
     if (keyring.forgetDevice) {
       keyring.forgetDevice();
-      this.persistAllKeyrings.bind(this)();
+      this.persistAllKeyrings();
       this._updateMemStoreKeyrings.bind(this)();
     } else {
       throw new Error(