[CrOS MultiDevice] Fix Setup Flow bug causing spurious setup attempts

The bug was caused by the change event on the password text field
triggering the event 'user-submitted-password' which causes a forward
navigate attempt. This fails if the password is wrong (this causes the
'incorrect password' issue in the bug) and succeeds if the password is
correct (this causes the spurious flow continuation issue).

Bug: 884965
Change-Id: I4ae9f9f9fd01901dacd9e69a216bdd3123eb9344
Reviewed-on: https://chromium-review.googlesource.com/1252503
Commit-Queue: Jordy Greenblatt <jordynass@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595219}

ui/webui/resources/cr_components/chromeos/multidevice_setup/password_page.html

@@ -40,7 +40,7 @@
             error-message="[[i18n('wrongPassword')]]"
             value="{{inputValue_}}"
             aria-disabled="false"
-            on-change="onUserPressedEnter_"
+            on-keypress="onInputKeypress_"
             autofocus>
         </cr-input>
       </div>

ui/webui/resources/cr_components/chromeos/multidevice_setup/password_page.js

@@ -138,8 +138,15 @@ Polymer({
     this.passwordInvalid_ = false;
   },
 
-  /** @private */
-  onUserPressedEnter_: function() {
+  /**
+   * @param {!Event} e
+   * @private
+   */
+  onInputKeypress_: function(e) {
+    // We are only listening for the user trying to enter their password.
+    if (e.key != 'Enter')
+      return;
+
     this.fire('user-submitted-password');
   },