Fixing a number of dart:html analyzer issues

tools/dom/templates/html/impl/impl_Geolocation.darttemplate

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of $LIBRARYNAME;
 
 @DocsEditable
 $(ANNOTATIONS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
 
   @DomName('Geolocation.getCurrentPosition')
@@ skipping 57 matching lines @@
         } else {
           assert(watchId != null);
           $dom_clearWatch(watchId);
         }
       });
 
     return controller.stream;
   }
 
   Geoposition _ensurePosition(domPosition) {
+$if DART2JS
     try {
       // Firefox may throw on this.
       if (domPosition is Geoposition) {
         return domPosition;
       }
     } catch(e) {}
     return new _GeopositionWrapper(domPosition);
+$else
+    return domPosition;
+$endif
   }
+
 $!MEMBERS}
 
 $if DART2JS
 /**
  * Wrapper for Firefox- it returns an object which we cannot map correctly.
  * Basically Firefox was returning a [xpconnect wrapped nsIDOMGeoPosition] but
  * which has further oddities.
  */
 class _GeopositionWrapper implements Geoposition {
   var _ptr;
   _GeopositionWrapper(this._ptr);
 
   Coordinates get coords => JS('Coordinates', '#.coords', _ptr);
   int get timestamp => JS('int', '#.timestamp', _ptr);
 }
 $endif