dart2js: add work-around hack for try.

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

Index: pkg/compiler/lib/src/js_emitter/program_builder.dart
diff --git a/pkg/compiler/lib/src/js_emitter/program_builder.dart b/pkg/compiler/lib/src/js_emitter/program_builder.dart
index 1bdfc8105e337045e07aa4fdf06c0a7b13ee18c9..4e2f55577e1f5162fdeb4978ad9e506d378751da 100644
--- a/pkg/compiler/lib/src/js_emitter/program_builder.dart
+++ b/pkg/compiler/lib/src/js_emitter/program_builder.dart
@@ -262,6 +262,28 @@ class ProgramBuilder {
                        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);