Ensure CheckInitialized is present independent of define.

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index edffca18f42c7e792da0857f512172b27238a315..0abc305596a2f368123352319f5df9561012937e 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -2921,14 +2921,12 @@ Local<Integer> Value::ToInteger() const {
 }
 
 
-#ifdef V8_ENABLE_CHECKS
-void i::Internals::CheckInitialized(v8::Isolate* external_isolate) {
+void i::Internals::CheckInitializedImpl(v8::Isolate* external_isolate) {
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(external_isolate);
   ApiCheck(isolate != NULL && isolate->IsInitialized() && !i::V8::IsDead(),
            "v8::internal::Internals::CheckInitialized()",
            "Isolate is not initialized or V8 has died");
 }
-#endif
 
 
 void External::CheckCast(v8::Value* that) {