Add option for outputting a deferred loading mapping.

pkg/compiler/lib/src/js_emitter/code_emitter_task.dart

Index: pkg/compiler/lib/src/js_emitter/code_emitter_task.dart
diff --git a/pkg/compiler/lib/src/js_emitter/code_emitter_task.dart b/pkg/compiler/lib/src/js_emitter/code_emitter_task.dart
index 6dcc012b766cf245b6efde8babe220ab256d4df1..e8e55e565f0cbbab4890688f0aeb13ab6b7db2c6 100644
--- a/pkg/compiler/lib/src/js_emitter/code_emitter_task.dart
+++ b/pkg/compiler/lib/src/js_emitter/code_emitter_task.dart
@@ -59,11 +59,11 @@ class CodeEmitterTask extends CompilerTask {
   jsAst.Expression isolateStaticClosureAccess(Element element) {
     return emitter.isolateStaticClosureAccess(element);
   }
-  
+
   jsAst.Expression isolateLazyInitializerAccess(Element element) {
     return emitter.isolateLazyInitializerAccess(element);
   }
-  
+
   jsAst.Expression generateEmbeddedGlobalAccess(String global) {
     return emitter.generateEmbeddedGlobalAccess(global);
   }
@@ -75,15 +75,15 @@ class CodeEmitterTask extends CompilerTask {
   jsAst.Expression staticFieldAccess(Element e) {
     return emitter.staticFunctionAccess(e);
   }
-  
+
   jsAst.Expression staticFunctionAccess(Element e) {
     return emitter.staticFunctionAccess(e);
   }
-  
+
   jsAst.Expression classAccess(Element e) {
     return emitter.classAccess(e);
   }
-  
+
   jsAst.Expression typedefAccess(Element e) {
     return emitter.typedefAccess(e);
   }
@@ -383,14 +383,14 @@ abstract class Emitter {
   jsAst.Expression generateEmbeddedGlobalAccess(String global);
   jsAst.Expression constantReference(ConstantValue value);
   jsAst.PropertyAccess staticFunctionAccess(Element element);
-  
+
   // TODO(zarah): Split into more fine-grained accesses.
-  /// Generates access to the js constructor of the class represented by 
+  /// Generates access to the js constructor of the class represented by
   /// [element]
   jsAst.PropertyAccess classAccess(Element element);
   jsAst.PropertyAccess typedefAccess(Element element);
   jsAst.PropertyAccess staticFieldAccess(Element element);
-  
+
 
   int compareConstants(ConstantValue a, ConstantValue b);
   bool isConstantInlinedOrAlreadyEmitted(ConstantValue constant);