Make built-ins strict mode conforming, and support a --use-strict flag.

src/debug-debugger.js

 // Copyright 2006-2008 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
 //       with the distribution.
 //     * Neither the name of Google Inc. nor the names of its
 //       contributors may be used to endorse or promote products derived
 //       from this software without specific prior written permission.
 //
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 // Default number of frames to include in the response to backtrace request.
-const kDefaultBacktraceLength = 10;
+var kDefaultBacktraceLength = 10;
 
-const Debug = {};
+var Debug = {};
 
 // Regular expression to skip "crud" at the beginning of a source line which is
 // not really code. Currently the regular expression matches whitespace and
 // comments.
-const sourceLineBeginningSkip = /^(?:\s*(?:\/\*.*?\*\/)*)*/;
+var sourceLineBeginningSkip = /^(?:\s*(?:\/\*.*?\*\/)*)*/;
 
 // Debug events which can occour in the V8 JavaScript engine. These originate
 // from the API include file debug.h.
 Debug.DebugEvent = { Break: 1,
                      Exception: 2,
                      NewFunction: 3,
                      BeforeCompile: 4,
                      AfterCompile: 5,
                      ScriptCollected: 6 };
 
@@ skipping 2559 matching lines @@
     case 'string':
     case 'number':
       json = value;
       break;
 
     default:
       json = null;
   }
   return json;
 }