[wasm] Keep all WebAssembly optimizations Isolate independent.

R=titzer@chromium.org

Change-Id: Ia2217d4f3ff9c8f1929ac622c96d6c4b75e6c091
Reviewed-on: https://chromium-review.googlesource.com/1072655Reviewed-by: Ben Titzer <titzer@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53367}

src/compiler/pipeline.cc

@@ -973,6 +973,8 @@ PipelineWasmCompilationJob::Status
 PipelineWasmCompilationJob::ExecuteJobImpl() {
   pipeline_.RunPrintAndVerify("Machine", true);
   if (FLAG_wasm_opt || asmjs_origin_) {
+    // WASM compilations must *always* be independent of the isolate.
+    Isolate* isolate = nullptr;
     PipelineData* data = &data_;
     PipelineRunScope scope(data, "wasm optimization");
     GraphReducer graph_reducer(scope.zone(), data->graph(),
@@ -981,9 +983,9 @@ PipelineWasmCompilationJob::ExecuteJobImpl() {
                                               data->common(), scope.zone());
     ValueNumberingReducer value_numbering(scope.zone(), data->graph()->zone());
     MachineOperatorReducer machine_reducer(data->mcgraph(), asmjs_origin_);
-    CommonOperatorReducer common_reducer(data->isolate(), &graph_reducer,
-                                         data->graph(), data->common(),
-                                         data->machine(), scope.zone());
+    CommonOperatorReducer common_reducer(isolate, &graph_reducer, data->graph(),
+                                         data->common(), data->machine(),
+                                         scope.zone());
     AddReducer(data, &graph_reducer, &dead_code_elimination);
     AddReducer(data, &graph_reducer, &machine_reducer);
     AddReducer(data, &graph_reducer, &common_reducer);