Bug 1559821 - teach JSContext about parse tasks r=jonco

Added a ParseTask pointer to JSContext, set/removed during ParseTask::runTask

Differential Revision: https://phabricator.services.mozilla.com/D35365

--HG--
extra : moz-landing-system : lando

js/src/vm/HelperThreads.cpp

@@ -428,6 +428,13 @@ struct MOZ_RAII AutoSetContextRuntime {
   ~AutoSetContextRuntime() { TlsContext.get()->setRuntime(nullptr); }
 };
 
+struct MOZ_RAII AutoSetContextParse {
+  explicit AutoSetContextParse(ParseTask* task) {
+    TlsContext.get()->setParseTask(task);
+  }
+  ~AutoSetContextParse() { TlsContext.get()->setParseTask(nullptr); }
+};
+
 static const JSClass parseTaskGlobalClass = {"internal-parse-task-global",
                                              JSCLASS_GLOBAL_FLAGS,
                                              &JS::DefaultGlobalClassOps};
@@ -494,6 +501,7 @@ void ParseTask::runTask() {
   JSRuntime* runtime = parseGlobal->runtimeFromAnyThread();
 
   AutoSetContextRuntime ascr(runtime);
+  AutoSetContextParse parsetask(this);
 
   Zone* zone = parseGlobal->zoneFromAnyThread();
   zone->setHelperThreadOwnerContext(cx);

js/src/vm/JSContext.h

@@ -74,6 +74,8 @@ struct AutoResolving;
 
 struct HelperThread;
 
+struct ParseTask;
+
 class InternalJobQueue : public JS::JobQueue {
  public:
   explicit InternalJobQueue(JSContext* cx)
@@ -177,6 +179,8 @@ struct JSContext : public JS::RootingContext,
 
   js::ThreadData<js::FreeOp> defaultFreeOp_;
 
+  js::ParseTask* parseTask_;
+
  public:
   // This is used by helper threads to change the runtime their context is
   // currently operating on.
@@ -332,6 +336,9 @@ struct JSContext : public JS::RootingContext,
   void setHelperThread(js::HelperThread* helperThread);
   js::HelperThread* helperThread() const { return helperThread_; }
 
+  void setParseTask(js::ParseTask* parseTask) { parseTask_ = parseTask; }
+  js::ParseTask* parseTask() const { return parseTask_; }
+
   bool isNurseryAllocSuppressed() const { return nurserySuppressions_; }
 
   // Threads may freely access any data in their realm, compartment and zone.