Use NSS_DISABLE_UNLOAD in valgrind and heapcheck scripts to avoid unsymbolized backtraces.

tools/valgrind/valgrind_webkit_tests.sh

 #!/bin/sh
 
-# Copyright (c) 2009 The Chromium Authors. All rights reserved.
+# Copyright (c) 2011 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Script to run layout tests under valgrind
 # Example:
 #  sh $0 LayoutTests/fast
 # Caveats:
 #  More of an example than a universal script.
 #  Must be run from src directory.
 #  Uses our standard suppressions; edit
@@ skipping 24 matching lines @@
 
 cat > vlayout-wrapper.sh <<"_EOF_"
 #!/bin/sh
 valgrind --suppressions=tools/valgrind/memcheck/suppressions.txt --tool=memcheck --smc-check=all --num-callers=30 --trace-children=yes --leak-check=full --show-possibly-lost=no --log-file=vlayout-%p.log --gen-suppressions=all --track-origins=yes "$@"
 _EOF_
 chmod +x vlayout-wrapper.sh
 
 rm -f vlayout-*.log
 export BROWSER_WRAPPER=`pwd`/vlayout-wrapper.sh
 export G_SLICE=always-malloc
+export NSS_DISABLE_UNLOAD=1
 export NSS_DISABLE_ARENA_FREE_LIST=1
 sh webkit/tools/layout_tests/run_webkit_tests.sh --run-singly -v --noshow-results --time-out-ms=200000 --nocheck-sys-deps --debug "$@"
 
 # Have to wait a bit for the output files to finish
 nfiles=`ls vlayout-*.log | wc -l`
 while true
 do
   ndone=`egrep -l "LEAK SUMMARY|no leaks are possible" vlayout-*.log | wc -l`
   if test $nfiles = $ndone
   then
     break
   fi
   echo "Waiting for valgrind to finish..."
   sleep 1
 done
 cat vlayout-*.log