Fix clang based build after r40969.

runtime/vm/intermediate_language.h

 // Copyright (c) 2013, 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_INTERMEDIATE_LANGUAGE_H_
 #define VM_INTERMEDIATE_LANGUAGE_H_
 
 #include "vm/allocation.h"
 #include "vm/ast.h"
 #include "vm/growable_array.h"
@@ skipping 1840 matching lines @@
 };
 
 
 struct BranchLabels {
   Label* true_label;
   Label* false_label;
   Label* fall_through;
 };
 
 
-struct InductionVariableInfo;
+class InductionVariableInfo;
 
 
 class PhiInstr : public Definition {
  public:
   PhiInstr(JoinEntryInstr* block, intptr_t num_inputs)
     : block_(block),
       inputs_(num_inputs),
       is_alive_(false),
       representation_(kTagged),
       reaching_defs_(NULL),
@@ skipping 6572 matching lines @@
       Isolate* isolate, bool opt) const {                                     \
     UNIMPLEMENTED();                                                          \
     return NULL;                                                              \
   }                                                                           \
   void Name::EmitNativeCode(FlowGraphCompiler* compiler) { UNIMPLEMENTED(); }
 
 
 }  // namespace dart
 
 #endif  // VM_INTERMEDIATE_LANGUAGE_H_