[debugger] implement per-function code coverage.

src/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 819 matching lines @@
         'crankshaft/lithium.h',
         'crankshaft/lithium-inl.h',
         'crankshaft/typing.cc',
         'crankshaft/typing.h',
         'crankshaft/unique.h',
         'date.cc',
         'date.h',
         'dateparser-inl.h',
         'dateparser.cc',
         'dateparser.h',
+        'debug/debug-coverage.cc',
+        'debug/debug-coverage.h',
         'debug/debug-evaluate.cc',
         'debug/debug-evaluate.h',
         'debug/debug-interface.h',
         'debug/debug-frames.cc',
         'debug/debug-frames.h',
         'debug/debug-scopes.cc',
         'debug/debug-scopes.h',
         'debug/debug.cc',
         'debug/debug.h',
         'debug/interface-types.h',
@@ skipping 1653 matching lines @@
       'conditions': [
         ['want_separate_host_toolset_mkpeephole==1', {
           'toolsets': ['host'],
         }, {
           'toolsets': ['target'],
         }],
       ],
     },
   ],
 }