Add --analyze-signatures-only option to dart2js

sdk/lib/_internal/compiler/implementation/resolution/members.dart

 // 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 resolution;
 
 abstract class TreeElements {
   Element operator[](Node node);
   Selector getSelector(Send send);
   Selector getGetterSelectorInComplexSendSet(SendSet node);
@@ skipping 345 matching lines @@
   }
 
   /// This method should only be used by this library (or tests of
   /// this library).
   ResolverVisitor visitorFor(Element element) {
     var mapping = new TreeElementMapping(element);
     return new ResolverVisitor(compiler, element, mapping);
   }
 
   void visitBody(ResolverVisitor visitor, Statement body) {
-    visitor.visit(body);
+    if (!compiler.analyzeSignaturesOnly) {
+      visitor.visit(body);
+    }
   }
 
   void resolveConstructorImplementation(FunctionElement constructor,
                                         FunctionExpression node) {
     if (!identical(constructor.defaultImplementation, constructor)) return;
     ClassElement intrface = constructor.getEnclosingClass();
     if (!intrface.isInterface()) return;
     DartType defaultType = intrface.defaultClass;
     if (defaultType == null) {
       error(node, MessageKind.NO_DEFAULT_CLASS,
@@ skipping 50 matching lines @@
     }
   }
 
   TreeElements resolveField(VariableElement element) {
     Node tree = element.parseNode(compiler);
     if(element.modifiers.isStatic() && element.variables.isTopLevel()) {
       error(element.modifiers.getStatic(),
             MessageKind.TOP_LEVEL_VARIABLE_DECLARED_STATIC);
     }
     ResolverVisitor visitor = visitorFor(element);
+    // TODO(johnniwinther): Avoid analyzing initializers if
+    // [Compiler.analyzeSignaturesOnly] is set.
     initializerDo(tree, visitor.visit);
 
     if (Elements.isStaticOrTopLevelField(element)) {
       if (tree.asSendSet() != null) {
         // TODO(ngeoffray): We could do better here by using the
         // constant handler to figure out if it's a lazy field or not.
         compiler.backend.registerLazyField();
       }
     }
 
@@ skipping 3360 matching lines @@
     return e;
   }
 
   /// Assumed to be called by [resolveRedirectingFactory].
   Element visitReturn(Return node) {
     Node expression = node.expression;
     return finishConstructorReference(visit(expression),
                                       expression, expression);
   }
 }