Refactor Subzero initialization and add a browser callback handler.

src/IceGlobalContext.h

 //===- subzero/src/IceGlobalContext.h - Global context defs -----*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file declares aspects of the compilation that persist across
@@ skipping 282 matching lines @@
   // no more work - the queue is empty and either end() has been
   // called or the Sequential flag was set.
   std::unique_ptr<Cfg> optQueueBlockingPop();
   // Notifies that no more work will be added to the work queue.
   void optQueueNotifyEnd() { OptQ.notifyEnd(); }
 
   void emitQueueBlockingPush(EmitterWorkItem *Item);
   EmitterWorkItem *emitQueueBlockingPop();
   void emitQueueNotifyEnd() { EmitQ.notifyEnd(); }
 
+  void initParserThread() {
+    ThreadContext *Tls = new ThreadContext();
+    auto Timers = getTimers();
+    Timers->initInto(Tls->Timers);
+    AllThreadContexts.push_back(Tls);
+    ICE_TLS_SET_FIELD(TLS, Tls);
+  }
+
   void startWorkerThreads() {
     size_t NumWorkers = getFlags().getNumTranslationThreads();
     auto Timers = getTimers();
     for (size_t i = 0; i < NumWorkers; ++i) {
       ThreadContext *WorkerTLS = new ThreadContext();
       Timers->initInto(WorkerTLS->Timers);
       AllThreadContexts.push_back(WorkerTLS);
       TranslationThreads.push_back(std::thread(
           &GlobalContext::translateFunctionsWrapper, this, WorkerTLS));
     }
@@ skipping 184 matching lines @@
   explicit OstreamLocker(GlobalContext *Ctx) : Ctx(Ctx) { Ctx->lockStr(); }
   ~OstreamLocker() { Ctx->unlockStr(); }
 
 private:
   GlobalContext *const Ctx;
 };
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICEGLOBALCONTEXT_H