Remove saving/restoring of the context at function entry.

runtime/vm/flow_graph_builder.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_FLOW_GRAPH_BUILDER_H_
 #define VM_FLOW_GRAPH_BUILDER_H_
 
 #include "platform/assert.h"
 #include "platform/globals.h"
 #include "vm/allocation.h"
@@ skipping 389 matching lines @@
       bool result_is_needed);
 
   StrictCompareInstr* BuildStrictCompare(AstNode* left,
                                          AstNode* right,
                                          Token::Kind kind,
                                          intptr_t token_pos);
 
   virtual void BuildTypeTest(ComparisonNode* node);
   virtual void BuildTypeCast(ComparisonNode* node);
 
-  bool MustSaveRestoreContext(SequenceNode* node) const;
+  bool HasContextScope() const;
 
   // Moves the nth parent context into the context register.
   void UnchainContexts(intptr_t n);
 
   void CloseFragment() { exit_ = NULL; }
 
   // Returns a local variable index for a temporary local that is
   // on top of the current expression stack.
   intptr_t GetCurrentTempLocalIndex() const;
 
@@ skipping 182 matching lines @@
   // Output parameters.
   GrowableArray<TargetEntryInstr**> true_successor_addresses_;
   GrowableArray<TargetEntryInstr**> false_successor_addresses_;
 
   intptr_t condition_token_pos_;
 };
 
 }  // namespace dart
 
 #endif  // VM_FLOW_GRAPH_BUILDER_H_