Revert "Don't use resultCode when handling SignIn result"

This reverts commit 0ccfa66.

packages/google_sign_in/android/src/main/java/io/flutter/plugins/googlesignin/GoogleSignInPlugin.java

@@ -492,13 +492,12 @@ public boolean onActivityResult(int requestCode, int resultCode, Intent data) {
           }
           return true;
         case REQUEST_CODE_SIGNIN:
-          // Whether resultCode is OK or not, the Task returned by GoogleSigIn will determine
-          // failure with better specifics which are extracted in onSignInResult method.
-          if (data != null) {
+          if (resultCode == Activity.RESULT_OK && data != null) {
             onSignInResult(GoogleSignIn.getSignedInAccountFromIntent(data));
+          } else if (resultCode == Activity.RESULT_CANCELED) {
+            finishWithError(ERROR_REASON_SIGN_IN_CANCELED, "User canceled sign in");
           } else {
-            // data is null which is highly unusual for a sign in result.
-            finishWithError(ERROR_REASON_SIGN_IN_FAILED, "Signin failed");
+            finishWithError(ERROR_REASON_STATUS, "Sign in failed with " + resultCode);
           }
           return true;
         default: