[wasm] Move ThreadInWasmScope out of trap-handler.h

{ThreadInWasmScope} in only used in a single location, which is in a
test. It does not look like many more such places will show up.

R=titzer@chromium.org,

Bug: v8:8015
Change-Id: I89f6f7e2bd13e2882e65f7657d73ba59a6c71757
Reviewed-on: https://chromium-review.googlesource.com/1193446
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55486}

src/trap-handler/trap-handler.h

@@ -100,12 +100,6 @@ inline void ClearThreadInWasm() {
   }
 }
 
-class ThreadInWasmScope {
- public:
-  ThreadInWasmScope() { SetThreadInWasm(); }
-  ~ThreadInWasmScope() { ClearThreadInWasm(); }
-};
-
 bool RegisterDefaultTrapHandler();
 V8_EXPORT_PRIVATE void RestoreOriginalSignalHandler();
 

test/cctest/wasm/wasm-run-utils.h

@@ -461,10 +461,12 @@ class WasmRunner : public WasmRunnerBase {
                                          wrapper_code, wrapper_.signature());
     int32_t result;
     {
-      trap_handler::ThreadInWasmScope scope;
+      trap_handler::SetThreadInWasm();
 
       result = runner.Call(static_cast<void*>(&p)...,
                            static_cast<void*>(&return_value));
+
+      trap_handler::ClearThreadInWasm();
     }
     CHECK_EQ(WASM_WRAPPER_RETURN_VALUE, result);
     return WasmRunnerBase::trap_happened