[NaCl SDK] Fix Linux builder breakage introduced by r243629.

I removed the PNACL_BIN variable from nacl_llvm.mk, which was used by the
Bullet demo in native_client_sdk/src/gonacl_appengine/src/bullet.

(No trybots, as this change is only run by the linux_nacl_sdk builder).

BUG=none
R=sbc@chromium.org

Review URL: https://codereview.chromium.org/132403009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244927 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 244927
drive: Replace FileCache::MarkDirty with OpenForWrite

IsOpenedForWrite() will be used to check if it's OK to clear dirty bit or not.

Replace MarkDirty() with OpenForWrite()
Add IsOpenedForWrite()
Change google_apis::RunTaskOnThread's argument type to SequencedTaskRunner to use it to run CloseForWrite().

BUG=326054
TEST=unit_tests

Review URL: https://codereview.chromium.org/133443002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244928 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 244928