[turbofan] Optimize string "length" property access based on types.

tools/gyp/v8.gyp

 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 501 matching lines @@
         '../../src/compiler/js-graph.cc',
         '../../src/compiler/js-graph.h',
         '../../src/compiler/js-inlining.cc',
         '../../src/compiler/js-inlining.h',
         '../../src/compiler/js-intrinsic-lowering.cc',
         '../../src/compiler/js-intrinsic-lowering.h',
         '../../src/compiler/js-operator.cc',
         '../../src/compiler/js-operator.h',
         '../../src/compiler/js-type-feedback.cc',
         '../../src/compiler/js-type-feedback.h',
+        '../../src/compiler/js-type-feedback-lowering.cc',
+        '../../src/compiler/js-type-feedback-lowering.h',
         '../../src/compiler/js-typed-lowering.cc',
         '../../src/compiler/js-typed-lowering.h',
         '../../src/compiler/jump-threading.cc',
         '../../src/compiler/jump-threading.h',
         '../../src/compiler/linkage-impl.h',
         '../../src/compiler/linkage.cc',
         '../../src/compiler/linkage.h',
         '../../src/compiler/liveness-analyzer.cc',
         '../../src/compiler/liveness-analyzer.h',
         '../../src/compiler/load-elimination.cc',
@@ skipping 1393 matching lines @@
         }],
         ['want_separate_host_toolset==1', {
           'toolsets': ['host'],
         }, {
           'toolsets': ['target'],
         }],
       ],
     },
   ],
 }