add a spinner to the login dialog

interface/resources/qml/LoginDialog/LinkAccountBody.qml

@@ -26,6 +26,7 @@ Item {
 
     function login() {
         mainTextContainer.visible = false
+        toggleLoading(true)
         loginDialog.login(usernameField.text, passwordField.text)
     }
 
@@ -59,6 +60,34 @@ Item {
         }
     }
 
+    function toggleLoading(isLoading) {
+        linkAccountSpinner.visible = isLoading
+        form.visible = !isLoading
+
+        if (loginDialog.isSteamRunning()) {
+            additionalInformation.visible = !isLoading
+        }
+
+        leftButton.visible = !isLoading
+        buttons.visible = !isLoading
+    }
+
+    BusyIndicator {
+        id: linkAccountSpinner
+
+        anchors {
+            top: parent.top
+            horizontalCenter: parent.horizontalCenter
+            topMargin: hifi.dimensions.contentSpacing.y
+        }
+
+        visible: false
+        running: true
+
+        width: 48
+        height: 48
+    }
+
     ShortcutText {
         id: mainTextContainer
         anchors {
@@ -266,6 +295,7 @@ Item {
         onHandleLoginFailed: {
             console.log("Login Failed")
             mainTextContainer.visible = true
+            toggleLoading(false)
         }
         onHandleLinkCompleted: {
             console.log("Link Succeeded")
@@ -276,7 +306,7 @@ Item {
         }
         onHandleLinkFailed: {
             console.log("Link Failed")
-
+            toggleLoading(false)
         }
     }