Make all tests pass ASAN.

Make all tests pass ASAN.

Unpoison additional locations touched by profiler's stack walking.
Use return value of Isolate::GetProfilerStackBounds.

Commands to build and test:

export CXX="third_party/clang/linux/bin/clang++ -fsanitize=address -fPIC"

gclient runhooks

./tools/build.py -m debug -a x64 runtime

ASAN_OPTIONS=handle_segv=0 python tools/test.py --report --time --mode=debug --arch=x64 --compiler=none --runtime=vm --failure-summary --write-debug-log --write-test-outcome-log --copy-coredumps --exclude-suite=pkg --checked
R=iposva@google.com

Committed: https://code.google.com/p/dart/source/detail?r=42635

[Ivan Posva, 2015-01-06 00:47:59]

LGTM -ip

[koda, 2015-01-06 15:44:29]

Committed patchset #2 (id:20001) manually as r42635 (presubmit successful).