[wasm] Turn field into local variable

R=titzer@chromium.org

Change-Id: Ib3b1cd479b42865420879bff9f1a83558585eb05
Reviewed-on: https://chromium-review.googlesource.com/c/1303301
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57072}

src/wasm/module-compiler.cc

@@ -855,18 +855,18 @@ class BackgroundCompileTask : public CancelableTask {
     // {OnBackgroundTaskStopped}.
     CompilationEnv env = native_module_->CreateCompilationEnv();
     auto* compilation_state = Impl(native_module_->compilation_state());
+    WasmFeatures detected_features = kNoWasmFeatures;
     while (!compilation_state->failed()) {
       if (!FetchAndExecuteCompilationUnit(&env, compilation_state,
-                                          &detected_features_)) {
+                                          &detected_features)) {
         break;
       }
     }
-    compilation_state->OnBackgroundTaskStopped(detected_features_);
+    compilation_state->OnBackgroundTaskStopped(detected_features);
   }
 
  private:
   NativeModule* const native_module_;
-  WasmFeatures detected_features_ = kNoWasmFeatures;
 };
 
 }  // namespace