DevTools: Fix the way source map treats single field segment in the very end of mappings.

Source/devtools/front_end/sdk/SourceMap.js

 /*
  * Copyright (C) 2012 Google Inc. 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
@@ skipping 251 matching lines @@
                 while (stringCharIterator.peek() === ";") {
                     lineNumber += 1;
                     columnNumber = 0;
                     stringCharIterator.next();
                 }
                 if (!stringCharIterator.hasNext())
                     break;
             }
 
             columnNumber += this._decodeVLQ(stringCharIterator);
-            if (this._isSeparator(stringCharIterator.peek())) {
+            if (!stringCharIterator.hasNext() || this._isSeparator(stringCharIterator.peek())) {
                 this._mappings.push([lineNumber, columnNumber]);
                 continue;
             }
 
             var sourceIndexDelta = this._decodeVLQ(stringCharIterator);
             if (sourceIndexDelta) {
                 sourceIndex += sourceIndexDelta;
                 sourceURL = sources[sourceIndex];
             }
             sourceLineNumber += this._decodeVLQ(stringCharIterator);
@@ skipping 81 matching lines @@
     },
 
     /**
      * @return {boolean}
      */
     hasNext: function()
     {
         return this._position < this._string.length;
     }
 }