No longer store the compilation-context in WorkItem.

pkg/compiler/lib/src/ssa/builder.dart

Index: pkg/compiler/lib/src/ssa/builder.dart
diff --git a/pkg/compiler/lib/src/ssa/builder.dart b/pkg/compiler/lib/src/ssa/builder.dart
index c23f3a6bfcf3f0dd5c3807e5e77fbb86ebc9b705..093344fc7baca529000835449c2cf8c5958974d6 100644
--- a/pkg/compiler/lib/src/ssa/builder.dart
+++ b/pkg/compiler/lib/src/ssa/builder.dart
@@ -39,6 +39,7 @@ import '../universe/use.dart' show DynamicUse, StaticUse, TypeUse;
 import '../util/util.dart';
 import '../world.dart' show ClassWorld;
 
+import 'context.dart';
 import 'graph_builder.dart';
 import 'locals_handler.dart';
 import 'nodes.dart';
@@ -79,14 +80,14 @@ class SsaBuilderTask extends CompilerTask {
 
   DiagnosticReporter get reporter => compiler.reporter;
 
-  HGraph build(CodegenWorkItem work) {
+  HGraph build(CodegenWorkItem work, SsaCompilationContext context) {
     return measure(() {
       Element element = work.element.implementation;
       return reporter.withCurrentElement(element, () {
         SsaBuilder builder = new SsaBuilder(
             work.element.implementation,
             work.resolvedAst,
-            work.compilationContext,
+            context,
             work.registry,
             backend,
             emitter.nativeEmitter,
@@ -117,7 +118,7 @@ class SsaBuilderTask extends CompilerTask {
           } else {
             name = "${element.name}";
           }
-          compiler.tracer.traceCompilation(name, work.compilationContext);
+          compiler.tracer.traceCompilation(name);
           compiler.tracer.traceGraph('builder', graph);
         }
         return graph;
@@ -370,7 +371,7 @@ class SsaBuilder extends ast.Visitor
 
   /// If not null, the builder will store in [context] data that is used later
   /// during the optimization phases.
-  final JavaScriptItemCompilationContext context;
+  final SsaCompilationContext context;
 
   /// Registry used to enqueue work during codegen, may be null to avoid
   /// enqueing any work.