[gapi.auth2] Fix prompt param type in GoogleAuth.signIn and similar methods

gapi.auth2/gapi.auth2-tests.ts

@@ -19,6 +19,13 @@ function test_getAuthInstance(){
   var auth = gapi.auth2.getAuthInstance();
 }
 
+function test_signIn(){
+  gapi.auth2.getAuthInstance().signIn({
+    scope: 'email profile',
+    prompt: 'content'
+  });
+}
+
 function test_getAuthResponse(){
   var user = gapi.auth2.getAuthInstance().currentUser.get();
   var authResponse = user.getAuthResponse();

gapi.auth2/index.d.ts

@@ -34,7 +34,7 @@ declare namespace gapi.auth2 {
     signIn(options?: {
       app_package_name?: string;
       fetch_basic_profile?: boolean;
-      prompt?: boolean;
+      prompt?: string;
       scope?: string;
     }, optionBuilder?: SigninOptionsBuilder): any;
 
@@ -62,7 +62,7 @@ declare namespace gapi.auth2 {
     attachClickHandler(container: any, options: {
       app_package_name?: string;
       fetch_basic_profile?: boolean;
-      prompt?: boolean;
+      prompt?: string;
       scope?: string;
     }, onsuccess: (googleUser: GoogleUser) => any, onfailure: (reason: string) => any): any;
   }
@@ -167,7 +167,7 @@ declare namespace gapi.auth2 {
     signIn(options?: {
       app_package_name?: string;
       fetch_basic_profile?: boolean;
-      prompt?: boolean;
+      prompt?: string;
       scope?: string;
     }, optionBuilder?: SigninOptionsBuilder): any;
 
@@ -177,7 +177,7 @@ declare namespace gapi.auth2 {
     grant(options?: {
       app_package_name?: string;
       fetch_basic_profile?: boolean;
-      prompt?: boolean;
+      prompt?: string;
       scope?: string;
     }, optionBuilder?: SigninOptionsBuilder): any;