[BACKPORT] A patch backported from chromium upstream

It could help address the crash issue when the number of TLS
slots reaches the max number.

See https://codereview.chromium.org/60743004
[Android] Use the Chromium TLS for thread local storage allocation

On Android ICS, the max number of thread local storage is limited to 64.
Chromium TLS provides a mechanism to support large number of TLS slots
which is independent of OS restictions.

This commit is to make sure the ThreadLocalPointer uses the Chromium TLS
mechnism instead of directly calling pthread_create_key, so that it can
avoid the crash if the number of TLS slots allocated exceeds the max number
allowed by OS.

BUG=https://crosswalk-project.org/jira/browse/XWALK-841
Merge pull request #107 from hmin/xwalkl-841

Fix the crash issue caused by no memory for TLS slot allocation