Fix use of history timers in background threads.

src/wasm/module-compiler.h

Index: src/wasm/module-compiler.h
diff --git a/src/wasm/module-compiler.h b/src/wasm/module-compiler.h
index 4f496c50e956655bf4fb77d78c0d459e2b698bee..2d66cb15b120bb08dcfa9736b99b4bf2144d0a5c 100644
--- a/src/wasm/module-compiler.h
+++ b/src/wasm/module-compiler.h
@@ -59,8 +59,7 @@ class ModuleCompiler {
 
   Isolate* isolate_;
   std::unique_ptr<WasmModule> module_;
-  std::shared_ptr<Counters> counters_shared_;
-  Counters* counters_;
+  const std::shared_ptr<Counters> counters_shared_;
   bool is_sync_;
   std::vector<std::unique_ptr<compiler::WasmCompilationUnit>>
       compilation_units_;
@@ -71,6 +70,8 @@ class ModuleCompiler {
   // This flag should only be set while holding result_mutex_.
   bool finisher_is_running_ = false;
 
+  Counters* counters() const { return counters_shared_.get(); }
+
   // Run by each compilation task and by the main thread. The
   // no_finisher_callback is called within the result_mutex_ lock when no
   // finishing task is running, i.e. when the finisher_is_running_ flag is not
@@ -156,8 +157,7 @@ class InstanceBuilder {
 
   Isolate* isolate_;
   WasmModule* const module_;
-  std::shared_ptr<Counters> counters_shared_;
-  Counters* counters_;
+  const std::shared_ptr<Counters> counters_shared_;
   ErrorThrower* thrower_;
   Handle<WasmModuleObject> module_object_;
   Handle<JSReceiver> ffi_;        // TODO(titzer): Use MaybeHandle
@@ -169,6 +169,8 @@ class InstanceBuilder {
   JSToWasmWrapperCache js_to_wasm_cache_;
   WeakCallbackInfo<void>::Callback instance_finalizer_callback_;
 
+  Counters* counters() const { return counters_shared_.get(); }
+
 // Helper routines to print out errors with imports.
 #define ERROR_THROWER_WITH_MESSAGE(TYPE)                                      \
   void Report##TYPE(const char* error, uint32_t index,                        \
@@ -260,8 +262,7 @@ class AsyncCompileJob {
 
  private:
   Isolate* isolate_;
-  std::shared_ptr<Counters> counters_shared_;
-  Counters* counters_;
+  const std::shared_ptr<Counters> counters_shared_;
   std::unique_ptr<byte[]> bytes_copy_;
   ModuleWireBytes wire_bytes_;
   Handle<Context> context_;
@@ -280,6 +281,8 @@ class AsyncCompileJob {
   size_t outstanding_units_ = 0;
   size_t num_background_tasks_ = 0;
 
+  Counters* counters() const { return counters_shared_.get(); }
+
   void ReopenHandlesInDeferredScope();
 
   void AsyncCompileFailed(ErrorThrower& thrower);