Change 'password' event to 'password-submitted' event.

This just clarifies the events intention.

BUG=303491
diff --git a/elements/viewer-password-screen/viewer-password-screen.html b/elements/viewer-password-screen/viewer-password-screen.html
index 64a8aeb..45c9481 100644
--- a/elements/viewer-password-screen/viewer-password-screen.html
+++ b/elements/viewer-password-screen/viewer-password-screen.html
@@ -42,7 +42,7 @@
       this.$.successMessage.style.color = 'rgb(0,0,0)';
       this.$.password.disabled = true;
       this.$.submit.disabled = true;
-      this.fire('password', { password: this.$.password.value });
+      this.fire('password-submitted', { password: this.$.password.value });
       return false;
     },
     activeChanged: function() {