Only record one in n line endings to save space.

src/rewriter.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/ast.h"
 #include "src/parser.h"
 #include "src/rewriter.h"
 #include "src/scopes.h"
@@ skipping 217 matching lines @@
     if (processor.HasStackOverflow()) return false;
 
     if (processor.result_assigned()) {
       DCHECK(function->end_position() != RelocInfo::kNoPosition);
       // Set the position of the assignment statement one character past the
       // source code, such that it definitely is not in the source code range
       // of an immediate inner scope. For example in
       //   eval('with ({x:1}) x = 1');
       // the end position of the function generated for executing the eval code
       // coincides with the end of the with scope which is the position of '1'.
+      // Note that this may mean the position is outside the source code
+      // completely if there is no terminal newline, curly brace, or semicolon,
+      // often the case for 'eval'.
       int pos = function->end_position();
       VariableProxy* result_proxy =
           processor.factory()->NewVariableProxy(result, pos);
       Statement* result_statement =
           processor.factory()->NewReturnStatement(result_proxy, pos);
       body->Add(result_statement, info->zone());
     }
   }
 
   return true;
 }
 
 
 }  // namespace internal
 }  // namespace v8