Support user generated custom native JS classes.

pkg/compiler/lib/src/js_backend/namer.dart

 // Copyright (c) 2011, 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 js_backend;
 
 /**
  * Assigns JavaScript identifiers to Dart variables, class-names and members.
  *
  * Names are generated through three stages:
@@ skipping 615 matching lines @@
   }
 
   /// Annotated name for [method] encoding arity and named parameters.
   jsAst.Name instanceMethodName(FunctionElement method) {
     if (method.isGenerativeConstructorBody) {
       return constructorBodyName(method);
     }
     return invocationName(new Selector.fromElement(method));
   }
 
+  String _jsNameHelper(Element e) {
+    if (e.jsInteropName != null && e.jsInteropName.isNotEmpty)
+      return e.jsInteropName;
+    return e.isLibrary ? 'self' : e.name;
+  }
+
+  String fixedBackendPath(Element element) {
+    if (!element.isJsInterop) return null;
+    if (element.isInstanceMember) return 'this';
+    if (element.isConstructor) return fixedBackendPath(element.enclosingClass);
+    if (element.isLibrary) return 'self';
+    var sb = new StringBuffer();
+    sb..write(_jsNameHelper(element.library));
+
+    if (element.enclosingClass != null && element.enclosingClass != element) {
+      sb..write('.')..write(_jsNameHelper(element.enclosingClass));
+    }
+    return sb.toString();
+  }
+
   /// Returns the annotated name for a variant of `call`.
   /// The result has the form:
   ///
   ///     call$<N>$namedParam1...$namedParam<M>
   ///
   /// This name cannot be minified because it is generated by string
   /// concatenation at runtime, by applyFunction in js_helper.dart.
   jsAst.Name deriveCallMethodName(List<String> suffix) {
     // TODO(asgerf): Avoid clashes when named parameters contain $ symbols.
     return new StringBackedName('$callPrefix\$${suffix.join(r'$')}');
@@ skipping 111 matching lines @@
 
   /**
    * Returns the JavaScript property name used to store an instance field.
    */
   jsAst.Name instanceFieldPropertyName(FieldElement element) {
     ClassElement enclosingClass = element.enclosingClass;
 
     if (element.hasFixedBackendName) {
       // Certain native fields must be given a specific name. Native names must
       // not contain '$'. We rely on this to avoid clashes.
+      // TODO(jacobr): we need to relax this constraint.
       assert(enclosingClass.isNative &&
              !element.fixedBackendName.contains(r'$'));
 
       return new StringBackedName(element.fixedBackendName);
     }
 
     // Instances of BoxFieldElement are special. They are already created with
     // a unique and safe name. However, as boxes are not really instances of
     // classes, the usual naming scheme that tries to avoid name clashes with
     // super classes does not apply. We still do not mark the name as a
@@ skipping 1205 matching lines @@
       }
     }
   }
 }
 
 enum NamingScope {
   global,
   instance,
   constant
 }