[wasm][eh] Install exception constructor unconditionally

WasmJs::Install uses command line flags for feature detection, because
the context is not yet available to detect origin trial flags.

Exception handling is available via an origin trial, so make sure that
the exception constructor is installed regardless of the command line
flag.

R=ahaas@chromium.org

Bug: chromium:1183026
Change-Id: Ie0950ce19adeafea6e46892098c9485d6f9da792
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2732022Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73223}

src/wasm/wasm-js.cc

@@ -2238,19 +2238,26 @@ void WasmJs::Install(Isolate* isolate, bool exposed_on_global_object) {
                         v8_str(isolate, "WebAssembly.Global"), ro_attributes);
 
   // Setup Exception
+  Handle<String> exception_name = v8_str(isolate, "Exception");
+  Handle<JSFunction> exception_constructor =
+      CreateFunc(isolate, exception_name, WebAssemblyException, true,
+                 SideEffectType::kHasSideEffect);
+  exception_constructor->shared().set_length(1);
   if (enabled_features.has_eh()) {
-    Handle<JSFunction> exception_constructor = InstallConstructorFunc(
-        isolate, webassembly, "Exception", WebAssemblyException);
-    context->set_wasm_exception_constructor(*exception_constructor);
-    SetDummyInstanceTemplate(isolate, exception_constructor);
-    JSFunction::EnsureHasInitialMap(exception_constructor);
-    Handle<JSObject> exception_proto(
-        JSObject::cast(exception_constructor->instance_prototype()), isolate);
-    Handle<Map> exception_map = isolate->factory()->NewMap(
-        i::WASM_EXCEPTION_OBJECT_TYPE, WasmExceptionObject::kHeaderSize);
-    JSFunction::SetInitialMap(exception_constructor, exception_map,
-                              exception_proto);
-  }
+    JSObject::AddProperty(isolate, webassembly, exception_name,
+                          exception_constructor, DONT_ENUM);
+  }
+  // Install the constructor on the context unconditionally so that it is also
+  // available when the feature is enabled via the origin trial.
+  context->set_wasm_exception_constructor(*exception_constructor);
+  SetDummyInstanceTemplate(isolate, exception_constructor);
+  JSFunction::EnsureHasInitialMap(exception_constructor);
+  Handle<JSObject> exception_proto(
+      JSObject::cast(exception_constructor->instance_prototype()), isolate);
+  Handle<Map> exception_map = isolate->factory()->NewMap(
+      i::WASM_EXCEPTION_OBJECT_TYPE, WasmExceptionObject::kHeaderSize);
+  JSFunction::SetInitialMap(exception_constructor, exception_map,
+                            exception_proto);
 
   // Setup Function
   if (enabled_features.has_type_reflection()) {