[builtins] FastNewFunctionContextStub becomes a builtin

src/builtins/builtins-constructor.h

 // Copyright 2016 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.
 
 #include "src/code-stub-assembler.h"
 
 namespace v8 {
 namespace internal {
 
 typedef compiler::Node Node;
 typedef compiler::CodeAssemblerState CodeAssemblerState;
 
 class ConstructorBuiltinsAssembler : public CodeStubAssembler {
  public:
   explicit ConstructorBuiltinsAssembler(CodeAssemblerState* state)
       : CodeStubAssembler(state) {}
 
   Node* EmitFastNewClosure(Node* shared_info, Node* context);
+  Node* EmitFastNewFunctionContext(Node* closure, Node* slots, Node* context,
+                                   ScopeType scope_type);
+  static int MaximumFunctionContextSlots();
+
+ private:
+  static const int kMaximumSlots = 0x8000;
+  static const int kSmallMaximumSlots = 10;
+
+  // FastNewFunctionContext can only allocate closures which fit in the
+  // new space.
+  STATIC_ASSERT(((kMaximumSlots + Context::MIN_CONTEXT_SLOTS) * kPointerSize +
+                 FixedArray::kHeaderSize) < kMaxRegularHeapObjectSize);
 };
 
 }  // namespace internal
 }  // namespace v8