adjustments to the colorer-out-of-sync gizmo

(the "()" in the bottom right of the drracket window)
  to make sure that it is right when switching tabs
  and when a frame is first opened

original commit: 0fe0858ba89477f9a07bd3e15c2dd55684906db8

collects/framework/private/color.rkt

@@ -137,7 +137,6 @@ added get-regions
                         (new paren-tree% (matches pairs))))
 
     (define lexer-states (list (make-new-lexer-state 0 'end)))
-
     (define/public (get-up-to-date?) 
       (andmap lexer-state-up-to-date? lexer-states))
 
@@ -246,6 +245,7 @@ added get-regions
         (on-lexer-valid lexers-all-valid?)))
     (define/pubment (on-lexer-valid valid?)
       (inner (void) on-lexer-valid valid?))
+    (define/public-final (is-lexer-valid?) lexers-all-valid?)
     
     (define/private (reset-tokens)
       (for-each

collects/scribblings/framework/color.scrbl

@@ -229,6 +229,10 @@
     The default method just returns @racket[(void)].
   }
   
+  @defmethod[#:mode public-final (is-lexer-valid?) boolean?]{
+    Indicates if the lexer is currently valid for this editor.
+  }
+  
 }
 @defmixin[color:text-mixin (text:basic<%>) (color:text<%>)]{
   Adds the functionality needed for on-the-fly coloring and parenthesis