dart2js: add work-around hack for try.

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

 // Copyright (c) 2014, 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 dart2js.js_emitter.program_builder;
 
 import 'js_emitter.dart' show computeMixinClass;
 import 'model.dart';
 
 import '../common.dart';
@@ skipping 244 matching lines @@
         .map(_buildClass)
         .toList(growable: false);
 
     bool visitStatics = true;
     List<Field> staticFieldsForReflection = _buildFields(library, visitStatics);
 
     return new Library(library, uri, statics, classes,
                        staticFieldsForReflection);
   }
 
+  /// HACK for Try.

[ahe, 2015/01/28 07:22:37]

This is not for Try Dart. This is for incremental compilation.

[floitsch, 2015/01/28 16:25:05]

Renamed function to buildClassWithFieldsForIncrementalCompilation
Done.

+  ///
+  /// Returns a class that contains the fields of a class.
+  Class buildClassWithFieldsForTry(ClassElement element) {
+    bool onlyForRti = _task.typeTestRegistry.rtiNeededClasses.contains(element);

[ahe, 2015/01/28 07:22:37]

For incremental compilation, this should probably always be false.

[floitsch, 2015/01/28 16:25:05]

Done.

+
+    List<Field> instanceFields =
+        onlyForRti ? const <Field>[] : _buildFields(element, false);
+
+    String name = namer.getNameOfClass(element);
+    String holderName = namer.globalObjectFor(element);
+    Holder holder = _registry.registerHolder(holderName);

[ahe, 2015/01/28 07:22:37]

I'm not sure I understand what a holder is. Does this help you generate only the
A-Z objects that are actually used?

[floitsch, 2015/01/28 16:25:05]

In the new emitter it's more complicated.
Since you don't need the holder I removed the code.

+    bool isInstantiated =
+        _compiler.codegenWorld.directlyInstantiatedClasses.contains(element);

[ahe, 2015/01/28 07:22:37]

For incremental compilation, my guess is that it would be better if this was
always true.

[floitsch, 2015/01/28 16:25:05]

Done.

+
+    return new Class(
+        element, name, holder, [], instanceFields, [], [], [], null,
+        isDirectlyInstantiated: isInstantiated,
+        onlyForRti: onlyForRti,

[ahe, 2015/01/28 07:22:37]

As mentioned above, the above two arguments should probably always have a fixed
value. This is because they are computed based on information that varies based
on how the program changes. Generally, those things are candidates for things
that should be avoided during incremental compilation.

[floitsch, 2015/01/28 16:25:05]

Done.

+        isNative: element.isNative);
+  }
+
   Class _buildClass(ClassElement element) {
     bool onlyForRti = _task.typeTestRegistry.rtiNeededClasses.contains(element);
 
     List<Method> methods = [];
     List<StubMethod> callStubs = <StubMethod>[];
 
     void visitMember(ClassElement enclosing, Element member) {
       assert(invariant(element, member.isDeclaration));
       assert(invariant(element, element == enclosing));
 
@@ skipping 205 matching lines @@
       _registry.registerConstant(outputUnit, constantValue);
       assert(!_constants.containsKey(constantValue));
       String name = namer.constantName(constantValue);
       String constantObject = namer.globalObjectForConstant(constantValue);
       Holder holder = _registry.registerHolder(constantObject);
       Constant constant = new Constant(name, holder, constantValue);
       _constants[constantValue] = constant;
     }
   }
 }