No longer store the compilation-context in WorkItem.

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

Index: pkg/compiler/lib/src/ssa/ssa_tracer.dart
diff --git a/pkg/compiler/lib/src/ssa/ssa_tracer.dart b/pkg/compiler/lib/src/ssa/ssa_tracer.dart
index 98978000fcd9337c2e2ada914902ff6645a3db78..d47e3ad2a8a558e1266569bb2673f67b74839b4b 100644
--- a/pkg/compiler/lib/src/ssa/ssa_tracer.dart
+++ b/pkg/compiler/lib/src/ssa/ssa_tracer.dart
@@ -19,10 +19,9 @@ import 'nodes.dart';
  */
 class HTracer extends HGraphVisitor with TracerUtil {
   Compiler compiler;
-  JavaScriptItemCompilationContext context;
   final EventSink<String> output;
 
-  HTracer(this.output, this.compiler, this.context);
+  HTracer(this.output, this.compiler);
 
   void traceGraph(String name, HGraph graph) {
     DEBUG_MODE = true;
@@ -76,7 +75,7 @@ class HTracer extends HGraphVisitor with TracerUtil {
 
   void visitBasicBlock(HBasicBlock block) {
     HInstructionStringifier stringifier =
-        new HInstructionStringifier(context, block, compiler);
+        new HInstructionStringifier(block, compiler);
     assert(block.id != null);
     tag("block", () {
       printProperty("name", "B${block.id}");
@@ -114,10 +113,9 @@ class HTracer extends HGraphVisitor with TracerUtil {
 
 class HInstructionStringifier implements HVisitor<String> {
   final Compiler compiler;
-  final JavaScriptItemCompilationContext context;
   final HBasicBlock currentBlock;
 
-  HInstructionStringifier(this.context, this.currentBlock, this.compiler);
+  HInstructionStringifier(this.currentBlock, this.compiler);
 
   visit(HInstruction node) => '${node.accept(this)} ${node.instructionType}';