Omit unreachable fall through code for graph intrinsics, e.g. Array.length.

runtime/vm/intrinsifier.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.
 // Class for intrinsifying functions.
 
 #ifndef VM_INTRINSIFIER_H_
 #define VM_INTRINSIFIER_H_
 
 #include "vm/allocation.h"
 #include "vm/method_recognizer.h"
 
 namespace dart {
 
 // Forward declarations.
 class Assembler;
 class FlowGraphCompiler;
 class Function;
 class TargetEntryInstr;
 class ParsedFunction;
 class FlowGraph;
 
 class Intrinsifier : public AllStatic {
  public:
-  static void Intrinsify(const ParsedFunction& parsed_function,
+  static bool Intrinsify(const ParsedFunction& parsed_function,
                          FlowGraphCompiler* compiler);
 #if defined(DART_NO_SNAPSHOT)
   static void InitializeState();
 #endif
 
   static bool GraphIntrinsify(const ParsedFunction& parsed_function,
                               FlowGraphCompiler* compiler);
 
   static intptr_t ParameterSlotFromSp();
 
@@ skipping 20 matching lines @@
 
   GRAPH_INTRINSICS_LIST(DECLARE_FUNCTION)
 
 #undef DECLARE_FUNCTION
 #endif
 };
 
 }  // namespace dart
 
 #endif  // VM_INTRINSIFIER_H_