Bug 1570259 part 5 - Remove AutoSetHelperThreadContext from off-thread Ion and Wasm tasks. r=tcampbell,luke

Off-thread tasks now use a pool of JSContexts (for compatibility with the XPCOM thread pool).
Tasks that don't need a JSContext can run without one (nullptr TlsContext). We can now do this
for Ion and Wasm tasks too.

Depends on D41380

Differential Revision: https://phabricator.services.mozilla.com/D41381

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

js/src/jit/IonBuilder.cpp

@@ -1144,7 +1144,6 @@ AbortReasonOr<Ok> IonBuilder::buildInline(IonBuilder* callerBuilder,
 void IonBuilder::runTask() {
   // This is the entry point when ion compiles are run offthread.
   JSRuntime* rt = script()->runtimeFromAnyThread();
-  AutoSetHelperThreadContext usesContext;
 
   TraceLoggerThread* logger = TraceLoggerForCurrentThread();
   TraceLoggerEvent event(TraceLogger_AnnotateScripts, script());

js/src/wasm/WasmGenerator.cpp

@@ -1259,10 +1259,7 @@ bool ModuleGenerator::finishTier2(const Module& module) {
   return module.finishTier2(*linkData_, std::move(codeTier));
 }
 
-void CompileTask::runTask() {
-  AutoSetHelperThreadContext needsContext;
-  ExecuteCompileTaskFromHelperThread(this);
-}
+void CompileTask::runTask() { ExecuteCompileTaskFromHelperThread(this); }
 
 size_t CompiledCode::sizeOfExcludingThis(
     mozilla::MallocSizeOf mallocSizeOf) const {

js/src/wasm/WasmModule.cpp

@@ -62,7 +62,6 @@ class Module::Tier2GeneratorTaskImpl : public Tier2GeneratorTask {
   void cancel() override { cancelled_ = true; }
 
   void runTask() override {
-    AutoSetHelperThreadContext usesContext;
     CompileTier2(*compileArgs_, bytecode_->bytes, *module_, &cancelled_);
   }
   ThreadType threadType() override {