dart2js: Only emit constructors of the native class interceptors that are used.

pkg/compiler/lib/src/js_backend/native_emitter.dart

Index: pkg/compiler/lib/src/js_backend/native_emitter.dart
diff --git a/pkg/compiler/lib/src/js_backend/native_emitter.dart b/pkg/compiler/lib/src/js_backend/native_emitter.dart
index 60f11553430e71639cbfa93dd9780a1d1020a973..2d25b240b2fe5160cfe068b7e42c3c84f614e381 100644
--- a/pkg/compiler/lib/src/js_backend/native_emitter.dart
+++ b/pkg/compiler/lib/src/js_backend/native_emitter.dart
@@ -232,10 +232,24 @@ class NativeEmitter {
     for (ClassElement classElement in classes) {
       if (!classElement.isNative) continue;
       if (neededClasses.contains(classElement)) {
+        ClassBuilder builder = builders[classElement];
+        // In CSP mode [emitClassConstructor] and [emitClassGettersSetters] have

[floitsch, 2015/01/15 15:14:40]

nit: newline before.

[zarah, 2015/01/16 08:48:50]

Done.

+        // a side-effect on "precompiled" functions in [OldEmitter]. For this
+        // reason, it is important that we don't call these methods before we
+        // are certain that a class is needed.
+
+        // [emitClassConstructor] only affects the generation of constructors
+        // in CSP mode.
+        emitterTask.oldEmitter.classEmitter.emitClassConstructor(
+            classElement, builder);
+        // [emitClassGettersSetters] does not affect whether or not a class is

[floitsch, 2015/01/15 15:14:40]

nit: newline before.

[zarah, 2015/01/16 08:48:50]

Done.

+        // needed. If getters/setters are emitted, the class has fields and
+        // is therefore non-trivial.
+        emitterTask.oldEmitter.classEmitter.emitClassGettersSetters(
+            classElement, builder);
         // Define interceptor class for [classElement].
         emitterTask.oldEmitter.classEmitter.emitClassBuilderWithReflectionData(
-            backend.namer.getNameOfClass(classElement),
-            classElement, builders[classElement],
+            backend.namer.getNameOfClass(classElement), classElement, builder,
             emitterTask.oldEmitter.getElementDescriptor(classElement));
         emitterTask.oldEmitter.needsClassSupport = true;
       }
@@ -301,13 +315,10 @@ class NativeEmitter {
     }
     builder.superName = superName;
 
-    emitterTask.oldEmitter.classEmitter.emitClassConstructor(
-        classElement, builder);
     bool hasFields = emitterTask.oldEmitter.classEmitter.emitFields(
         classElement, builder, classIsNative: true);
     int propertyCount = builder.properties.length;
-    emitterTask.oldEmitter.classEmitter.emitClassGettersSetters(
-        classElement, builder);
+
     emitterTask.oldEmitter.classEmitter.emitInstanceMembers(
         classElement, builder);
     emitterTask.oldEmitter.typeTestEmitter.emitIsTests(classElement, builder);