[es6] Add a flag to the Isolate that defines whether ES2015 tail call elimination is enabled or not.

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 1071 matching lines @@
 
   BasicBlockProfiler* GetOrCreateBasicBlockProfiler();
   BasicBlockProfiler* basic_block_profiler() { return basic_block_profiler_; }
 
   std::string GetTurboCfgFileName();
 
 #if TRACE_MAPS
   int GetNextUniqueSharedFunctionInfoId() { return next_unique_sfi_id_++; }
 #endif
 
+  // Support for dynamically disabling tail call elimination.
+  Address is_tail_call_elimination_enabled_address() {
+    return reinterpret_cast<Address>(&is_tail_call_elimination_enabled_);
+  }
+  bool is_tail_call_elimination_enabled() const {
+    return is_tail_call_elimination_enabled_;
+  }
+  void set_tail_call_elimination_enabled(bool enabled) {
+    is_tail_call_elimination_enabled_ = enabled;
+  }
 
   void AddDetachedContext(Handle<Context> context);
   void CheckDetachedContextsAfterGC();
 
   List<Object*>* partial_snapshot_cache() { return &partial_snapshot_cache_; }
 
   void set_array_buffer_allocator(v8::ArrayBuffer::Allocator* allocator) {
     array_buffer_allocator_ = allocator;
   }
   v8::ArrayBuffer::Allocator* array_buffer_allocator() const {
@@ skipping 168 matching lines @@
 
   // Whether the isolate has been created for snapshotting.
   bool serializer_enabled_;
 
   // True if fatal error has been signaled for this isolate.
   bool has_fatal_error_;
 
   // True if this isolate was initialized from a snapshot.
   bool initialized_from_snapshot_;
 
+  // True if ES2015 tail call elimination feature is enabled.
+  bool is_tail_call_elimination_enabled_;
+
   // Time stamp at initialization.
   double time_millis_at_init_;
 
 #ifdef DEBUG
   // A static array of histogram info for each type.
   HistogramInfo heap_histograms_[LAST_TYPE + 1];
   JSObject::SpillInformation js_spill_information_;
 #endif
 
   Debug* debug_;
@@ skipping 292 matching lines @@
 
   EmbeddedVector<char, 128> filename_;
   FILE* file_;
   int scope_depth_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_ISOLATE_H_