Use closure tracer to identify closures that are not passed to Function.apply

sdk/lib/_internal/compiler/implementation/closure.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.
 
 library closureToClassMapper;
 
 import "elements/elements.dart";
 import "dart2jslib.dart";
 import "dart_types.dart";
 import "scanner/scannerlib.dart" show Token;
 import "tree/tree.dart";
 import "util/util.dart";
-import "elements/modelx.dart" show ElementX, FunctionElementX, ClassElementX;
+import "elements/modelx.dart" show ElementX, SynthesizedCallMethodElementX,
+    ClassElementX;
 import "elements/visitor.dart" show ElementVisitor;
 
 class ClosureNamer {
   String getClosureVariableName(String name, int id) {
     return "${name}_$id";
   }
 }
 
 class ClosureTask extends CompilerTask {
   Map<Node, ClosureClassMap> closureMappingCache;
@@ skipping 116 matching lines @@
     callType = methodElement.type;
   }
 
   bool isClosure() => true;
 
   Token position() => node.getBeginToken();
 
   Node parseNode(DiagnosticListener listener) => node;
 
   /**
-   * The most outer method this closure is declared into.
+   * The element for the declaration of the function expression.
    */
   final TypedElement methodElement;
 
   // A [ClosureClassElement] is nested inside a function or initializer in terms
   // of [enclosingElement], but still has to be treated as a top-level
   // element.
   bool isTopLevel() => true;
 
   get enclosingElement => methodElement;
 
@@ skipping 548 matching lines @@
     parts.printOn(sb, '_');
     return sb.toString();
   }
 
   ClosureClassMap globalizeClosure(FunctionExpression node,
                                    TypedElement element) {
     String closureName = computeClosureName(element);
     ClassElement globalizedElement = new ClosureClassElement(
         node, closureName, compiler, element, element.getCompilationUnit());
     FunctionElement callElement =
-        new FunctionElementX.from(Compiler.CALL_OPERATOR_NAME,
-                                  element,
-                                  globalizedElement);
+        new SynthesizedCallMethodElementX(Compiler.CALL_OPERATOR_NAME,
+                                          element,
+                                          globalizedElement);
     ClosureContainer enclosing = element.enclosingElement;
     enclosing.nestedClosures.add(callElement);
     globalizedElement.addMember(callElement, compiler);
     // The nested function's 'this' is the same as the one for the outer
     // function. It could be [null] if we are inside a static method.
     Element thisElement = closureData.thisElement;
     return new ClosureClassMap(element, globalizedElement,
                                callElement, thisElement);
   }
 
@@ skipping 99 matching lines @@
   }
 
   visitTryStatement(TryStatement node) {
     // TODO(ngeoffray): implement finer grain state.
     bool oldInTryStatement = inTryStatement;
     inTryStatement = true;
     node.visitChildren(this);
     inTryStatement = oldInTryStatement;
   }
 }