[wasm] Remove dead code from runtime stack walks.

R=clemensh@chromium.org

Change-Id: Iabbef9d054671ec11a48321bb4e75a49084560ed
Reviewed-on: https://chromium-review.googlesource.com/1238925Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56198}

src/runtime/runtime-wasm.cc

@@ -29,15 +29,10 @@ Context* GetNativeContextFromWasmInstanceOnStackTop(Isolate* isolate) {
   // On top: C entry stub.
   DCHECK_EQ(StackFrame::EXIT, it.frame()->type());
   it.Advance();
-  // Next: the wasm (compiled or interpreted) frame.
-  WasmInstanceObject* instance = nullptr;
-  if (it.frame()->is_wasm_compiled()) {
-    instance = WasmCompiledFrame::cast(it.frame())->wasm_instance();
-  } else {
-    DCHECK(it.frame()->is_wasm_interpreter_entry());
-    instance = WasmInterpreterEntryFrame::cast(it.frame())->wasm_instance();
-  }
-  return instance->native_context();
+  // Next: the wasm compiled frame.
+  DCHECK(it.frame()->is_wasm_compiled());
+  WasmCompiledFrame* frame = WasmCompiledFrame::cast(it.frame());
+  return frame->wasm_instance()->native_context();
 }
 
 class ClearThreadInWasmScope {