[runtime] Rewrite Function.prototype.toString in C++.

src/objects.h

 // Copyright 2015 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_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include <iosfwd>
 
 #include "src/allocation.h"
@@ skipping 7392 matching lines @@
 
   // The function's name if it is configured, otherwise shared function info
   // debug name.
   static Handle<String> GetName(Handle<JSFunction> function);
 
   // The function's displayName if it is set, otherwise name if it is
   // configured, otherwise shared function info
   // debug name.
   static Handle<String> GetDebugName(Handle<JSFunction> function);
 
+  // The function's string representation implemented according to
+  // ES6 section 19.2.3.5 Function.prototype.toString ( ).
+  static Handle<String> ToString(Handle<JSFunction> function);
+
   // Layout descriptors. The last property (from kNonWeakFieldsEndOffset to
   // kSize) is weak and has special handling during garbage collection.
   static const int kPrototypeOrInitialMapOffset = JSObject::kHeaderSize;
   static const int kSharedFunctionInfoOffset =
       kPrototypeOrInitialMapOffset + kPointerSize;
   static const int kContextOffset = kSharedFunctionInfoOffset + kPointerSize;
   static const int kLiteralsOffset = kContextOffset + kPointerSize;
   static const int kNonWeakFieldsEndOffset = kLiteralsOffset + kPointerSize;
   static const int kCodeEntryOffset = kNonWeakFieldsEndOffset;
   static const int kNextFunctionLinkOffset = kCodeEntryOffset + kPointerSize;
@@ skipping 3285 matching lines @@
     }
     return value;
   }
 };
 
 
 }  // NOLINT, false-positive due to second-order macros.
 }  // NOLINT, false-positive due to second-order macros.
 
 #endif  // V8_OBJECTS_H_