Make CTX allocatable by the register allocator.

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 407 matching lines @@
   // on top of the current expression stack.
   intptr_t GetCurrentTempLocalIndex() const;
 
   Value* BuildObjectAllocation(ConstructorCallNode* node);
   void BuildConstructorCall(ConstructorCallNode* node,
                             PushArgumentInstr* alloc_value);
 
   void BuildSaveContext(const LocalVariable& variable);
   void BuildRestoreContext(const LocalVariable& variable);
 
+  Definition* BuildStoreContext(Value* value);
+  Definition* BuildCurrentContext();
+
   void BuildThrowNode(ThrowNode* node);
 
   StaticCallInstr* BuildStaticNoSuchMethodCall(
       const Class& target_class,
       AstNode* receiver,
       const String& method_name,
       ArgumentListNode* method_arguments,
       bool save_last_arg,
       bool is_super_invocation);
 
@@ skipping 162 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_