Set up isolate in CFXJS_Engine's constructor

fxjs/fxjs_v8_embeddertest.cpp

Index: fxjs/fxjs_v8_embeddertest.cpp
diff --git a/fxjs/fxjs_v8_embeddertest.cpp b/fxjs/fxjs_v8_embeddertest.cpp
index 2da313192dd7f04091d80edfa2a2fea461e48e1e..a877a36e56ba8c40af7e9b406da17d53c0e27dd7 100644
--- a/fxjs/fxjs_v8_embeddertest.cpp
+++ b/fxjs/fxjs_v8_embeddertest.cpp
@@ -45,12 +45,10 @@ TEST_F(FXJSV8EmbedderTest, MultipleEngines) {
   v8::Isolate::Scope isolate_scope(isolate());
   v8::HandleScope handle_scope(isolate());
 
-  CFXJS_Engine engine1;
-  engine1.SetIsolate(isolate());
+  CFXJS_Engine engine1(isolate());
   engine1.InitializeEngine();
 
-  CFXJS_Engine engine2;
-  engine2.SetIsolate(isolate());
+  CFXJS_Engine engine2(isolate());
   engine2.InitializeEngine();
 
   v8::Context::Scope context_scope(GetV8Context());