PPAPI: Implement PPB_FileMapping on POSIX

BUG=83774
R=bbudge@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=247473

Review URL: https://codereview.chromium.org/69663002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@247546 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 247546
Revert of [Android] Re-enable content_browsertests on main waterfall.  (https://codereview.chromium.org/132403005/)

Reason for revert:
content_browsertests have been crashy and flaky since being re-enabled.

Looks like they crashing on shutdown, but I'm not sure.

Failed:
http://build.chromium.org/p/chromium.linux/builders/Android%20Tests/builds/11552
http://build.chromium.org/p/chromium.linux/builders/Android%20Tests/builds/11554

On this one, content_browsertests crashed but still passed. This caused INJECT_EVENTS exceptions in later tests.
http://build.chromium.org/p/chromium.linux/builders/Android%20Tests%20%28dbg%29/builds/18163

We see the same thing downstream.


Original issue's description:
> [Android] Re-enable content_browsertests on main waterfall.
> 
> There's enough infra capacity now.
> 
> BUG=
> R=navabi@chromium.org, navabi@google.com
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=247341

TBR=navabi@chromium.org,navabi@google.com,frankf@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=

Review URL: https://codereview.chromium.org/135363005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@247547 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 247547