Remove a bunch of Isolate::UncheckedCurrent calls

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index 04327b1b2cce83b8cc76cc69be58928e9ae5e5cb..14a0d46726b8eadf523012a62dd1c03852330fba 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -2053,16 +2053,6 @@ void Isolate::Enter() {
     }
   }
 
-  // Threads can have default isolate set into TLS as Current but not yet have
-  // PerIsolateThreadData for it, as it requires more advanced phase of the
-  // initialization. For example, a thread might be the one that system used for
-  // static initializers - in this case the default isolate is set in TLS but
-  // the thread did not yet Enter the isolate. If PerisolateThreadData is not
-  // there, use the isolate set in TLS.
-  if (current_isolate == NULL) {
-    current_isolate = Isolate::UncheckedCurrent();
-  }
-
   PerIsolateThreadData* data = FindOrAllocatePerThreadDataForThisThread();
   ASSERT(data != NULL);
   ASSERT(data->isolate_ == this);