[turbofan] Simply context specialization and fix for OSR.

src/compiler/ast-graph-builder.h

Index: src/compiler/ast-graph-builder.h
diff --git a/src/compiler/ast-graph-builder.h b/src/compiler/ast-graph-builder.h
index 515283fc8a48fabde62cce0b7959e3e1552b98fa..ebeb6c613c9c817d10f01927970a5067eec77e87 100644
--- a/src/compiler/ast-graph-builder.h
+++ b/src/compiler/ast-graph-builder.h
@@ -31,7 +31,7 @@ class AstGraphBuilder : public AstVisitor {
                   LoopAssignmentAnalysis* loop_assignment = NULL);
 
   // Creates a graph by visiting the entire AST.
-  bool CreateGraph();
+  bool CreateGraph(bool constant_context);
 
   // Helpers to create new control nodes.
   Node* NewIfTrue() { return NewNode(common()->IfTrue()); }
@@ -51,12 +51,6 @@ class AstGraphBuilder : public AstVisitor {
   // Visiting function for declarations list is overridden.
   void VisitDeclarations(ZoneList<Declaration*>* declarations) OVERRIDE;
 
-  // Get the node that represents the outer function context.
-  Node* GetFunctionContext();
-
-  // Get the node that represents the outer function closure.
-  Node* GetFunctionClosure();
-
  private:
   class AstContext;
   class AstEffectContext;
@@ -88,7 +82,7 @@ class AstGraphBuilder : public AstVisitor {
 
   // Nodes representing values in the activation record.
   SetOncePointer<Node> function_closure_;
-  Node* function_context_;
+  SetOncePointer<Node> function_context_;
 
   // Temporary storage for building node input lists.
   int input_buffer_size_;
@@ -127,8 +121,15 @@ class AstGraphBuilder : public AstVisitor {
   void set_execution_context(ContextScope* ctx) { execution_context_ = ctx; }
   void set_exit_control(Node* exit) { exit_control_ = exit; }
 
+  // Create the main graph body by visiting the AST.
   void CreateGraphBody();
 
+  // Create the node that represents the outer context of the function.
+  void CreateFunctionContext(bool constant_context);
+
+  // Get or create the node that represents the outer function closure.
+  Node* GetFunctionClosure();
+
   // Node creation helpers.
   Node* NewNode(const Operator* op, bool incomplete = false) {
     return MakeNode(op, 0, static_cast<Node**>(NULL), incomplete);