Use integer session ID in MediaDrmBridge.

This is part of the effort to move to EME WD implementation. In Chromium, we use
an integer "session ID" to track all EME MediaKeySession calls. This CL updates
MediaDrmBridge to do so. Internally, we uses a ByteBuffer <-> int mapping to
track MediaDrm sessions and EME session IDs.

Also, we use ByteBuffer instead of String to track internal sessions. This
eliminates seveval cases of UnsupportedEncodingException catching since we don't
need to do byte[] <-> String conversion anymore.

R=jrummell@chromium.org,qinmin@chromium.org
BUG=224786
TEST=EME test pages still work on Chrome for Android.

Review URL: https://codereview.chromium.org/107793002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@239903 0039d316-1c4b-4281-b951-d872f2087c98
cc: Add PRESUBMIT rule to ban using cc:: inside of namespace cc {...}

This also makes cc/ PRESUBMIT clean for the new check.

The most invasive changes were:

1. Moving the cc/test/paths.h enum into a CCPaths class (named with
CC prefix to clarify this path is for CC since the enum is extending
an enum from base/.
2. Merge ResourcePool::Resource up into ScopedResource which was the
same thing basically.

R=enne
BUG=

Review URL: https://codereview.chromium.org/109263003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@239904 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 239904