Revert of Get rid of UnsafeCurrent in Sampler

src/isolate.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_ISOLATE_H_
 #define V8_ISOLATE_H_
 
 #include <queue>
 #include <set>
 
@@ skipping 477 matching lines @@
 
   // Returns the isolate inside which the current thread is running.
   INLINE(static Isolate* Current()) {
     DCHECK(base::NoBarrier_Load(&isolate_key_created_) == 1);
     Isolate* isolate = reinterpret_cast<Isolate*>(
         base::Thread::GetExistingThreadLocal(isolate_key_));
     DCHECK(isolate != NULL);
     return isolate;
   }
 
+  // Like Current, but skips the check that |isolate_key_| was initialized.
+  // Callers have to ensure that themselves.
+  // DO NOT USE. The only remaining callsite will be deleted soon.
+  INLINE(static Isolate* UnsafeCurrent()) {
+    return reinterpret_cast<Isolate*>(
+        base::Thread::GetThreadLocal(isolate_key_));
+  }
+
   // Usually called by Init(), but can be called early e.g. to allow
   // testing components that require logging but not the whole
   // isolate.
   //
   // Safe to call more than once.
   void InitializeLoggingAndCounters();
 
   bool Init(Deserializer* des);
 
   // True if at least one thread Enter'ed this isolate.
@@ skipping 1072 matching lines @@
 
   EmbeddedVector<char, 128> filename_;
   FILE* file_;
   int scope_depth_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_ISOLATE_H_