No longer store the compilation-context in WorkItem.

pkg/compiler/lib/src/tracer.dart

Index: pkg/compiler/lib/src/tracer.dart
diff --git a/pkg/compiler/lib/src/tracer.dart b/pkg/compiler/lib/src/tracer.dart
index 21d2ed5c9d3d8cb66937f1bb3ff46c5a214565d1..e73e82aa63718861a99730ae4276eecedd34731b 100644
--- a/pkg/compiler/lib/src/tracer.dart
+++ b/pkg/compiler/lib/src/tracer.dart
@@ -7,7 +7,6 @@ library tracer;
 import 'dart:async' show EventSink;
 
 import '../compiler.dart' as api;
-import 'common/work.dart' show ItemCompilationContext;
 import 'compiler.dart' show Compiler;
 import 'ssa/nodes.dart' as ssa show HGraph;
 import 'ssa/ssa_tracer.dart' show HTracer;
@@ -28,7 +27,6 @@ final RegExp TRACE_FILTER =
  */
 class Tracer extends TracerUtil {
   final Compiler compiler;
-  ItemCompilationContext context;
   bool traceActive = false;
   final EventSink<String> output;
   final bool isEnabled = TRACE_FILTER != null;
@@ -37,12 +35,10 @@ class Tracer extends TracerUtil {
       : this.compiler = compiler,
         output = TRACE_FILTER != null ? outputProvider('dart', 'cfg') : null;
 
-  void traceCompilation(
-      String methodName, ItemCompilationContext compilationContext) {
+  void traceCompilation(String methodName) {
     if (!isEnabled) return;
     traceActive = TRACE_FILTER.hasMatch(methodName);
     if (!traceActive) return;
-    this.context = compilationContext;
     tag("compilation", () {
       printProperty("name", methodName);
       printProperty("method", methodName);
@@ -53,7 +49,7 @@ class Tracer extends TracerUtil {
   void traceGraph(String name, var irObject) {
     if (!traceActive) return;
     if (irObject is ssa.HGraph) {
-      new HTracer(output, compiler, context).traceGraph(name, irObject);
+      new HTracer(output, compiler).traceGraph(name, irObject);
     }
   }