cps-ir: Set runtime type information for new objects that require it.

pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.dart

Index: pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.dart
diff --git a/pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.dart b/pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.dart
index ef33a135f4deaf41d3d735f9f4bd12fb948c0ff8..a002d6ee9829bee357984ab2f83ccb21f4d081ea 100644
--- a/pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.dart
+++ b/pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.dart
@@ -1283,6 +1283,19 @@ class DartIrBuilderVisitor extends IrBuilderVisitor {
   }
 }
 
+/// The [IrBuilder]s view on the information about the program that has been
+/// computed in resolution and and type interence.
+class GlobalProgramInformation {
+  final Compiler _compiler;
+  JavaScriptBackend get _backend => _compiler.backend;
+
+  GlobalProgramInformation(this._compiler);
+
+  /// Returns [true], if the analysis could not determine that the type
+  /// arguments for the class [cls] are never used in the program.
+  bool requiresRuntimeTypesFor(ClassElement cls) => _backend.classNeedsRti(cls);
+}
+
 /// IR builder specific to the JavaScript backend, coupled to the [JsIrBuilder].
 class JsIrBuilderVisitor extends IrBuilderVisitor {
   /// Promote the type of [irBuilder] to [JsIrBuilder].
@@ -1428,6 +1441,13 @@ class JsIrBuilderVisitor extends IrBuilderVisitor {
     return visitor.withBuilder(irBuilder, () => visitor.translateConstant(exp));
   }
 
+  JsIrBuilder getBuilderFor(Element element) {
+    return new JsIrBuilder(
+        new GlobalProgramInformation(compiler),
+        compiler.backend.constantSystem,
+        element);
+  }
+
   /// Builds the IR for a given constructor.
   ///
   /// 1. Evaluates all own or inherited field initializers.
@@ -1438,8 +1458,7 @@ class JsIrBuilderVisitor extends IrBuilderVisitor {
     constructor = constructor.implementation;
     ClassElement classElement = constructor.enclosingClass.implementation;
 
-    JsIrBuilder builder =
-        new JsIrBuilder(compiler.backend.constantSystem, constructor);
+    JsIrBuilder builder = getBuilderFor(constructor);
 
     return withBuilder(builder, () {
       // Setup parameters and create a box if anything is captured.
@@ -1704,8 +1723,7 @@ class JsIrBuilderVisitor extends IrBuilderVisitor {
         node,
         elements);
 
-    JsIrBuilder builder =
-        new JsIrBuilder(compiler.backend.constantSystem, body);
+    JsIrBuilder builder = getBuilderFor(body);
 
     return withBuilder(builder, () {
       irBuilder.buildConstructorBodyHeader(getConstructorBodyParameters(body),
@@ -1727,8 +1745,7 @@ class JsIrBuilderVisitor extends IrBuilderVisitor {
         element,
         node,
         elements);
-    IrBuilder builder =
-        new JsIrBuilder(compiler.backend.constantSystem, element);
+    IrBuilder builder = getBuilderFor(element);
     return withBuilder(builder, () => _makeFunctionBody(element, node));
   }