Dart2js option to dump info about compilation

sdk/lib/_internal/compiler/implementation/js_backend/backend.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 js_backend;
 
 const VERBOSE_OPTIMIZER_HINTS = false;
 
 class JavaScriptItemCompilationContext extends ItemCompilationContext {
   final Set<HInstruction> boundsChecked = new Set<HInstruction>();
@@ skipping 1899 matching lines @@
     }
     if (hasNoThrows && !hasNoInline) {
       compiler.internalErrorOnElement(
           element, "@NoThrows() should always be combined with @NoInline");
     }
     if (hasNoSideEffects && !hasNoInline) {
       compiler.internalErrorOnElement(
           element, "@NoSideEffects() should always be combined with @NoInline");
     }
   }
+
+  CodeBuffer codeOf(Element element) {
+    return generatedCode.containsKey(element)
+        ? jsAst.prettyPrint(generatedCode[element], compiler)
+        : null;
+  }
 }
 
 /// Records that [constant] is used by [user.element].
 class Dependency {
   final Constant constant;
   final TreeElements user;
 
   const Dependency(this.constant, this.user);
 }
 
@@ skipping 38 matching lines @@
     copy(constant.values);
     copy(constant.protoValue);
     copy(constant);
   }
 
   void visitConstructed(ConstructedConstant constant) {
     copy(constant.fields);
     copy(constant);
   }
 }