Add support for user-level Native Messaging hosts installation.

With this change Native Messaging hosts can be installed into user's
directory without requiring admin permissions

BUG=237873
R=asvitkine@chromium.org, dconnelly@chromium.org, jschuh@chromium.org, kalman@chromium.org
TBR=mattm@chromium.org

Review URL: https://codereview.chromium.org/140583002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@247299 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 247299
[NaCl SDK] Add fflush to nacl_io demo

R=binji@chromium.org

Review URL: https://codereview.chromium.org/139823002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@247300 0039d316-1c4b-4281-b951-d872f2087c98
Convert Media Galleries to use base::File

Unfortunately, this brings in changes to webkit/browser/fileapi, and once
that changes, a lot of files have to be updated.

The bright side is that most of the collateral changes are just trivial
renaming of PlatformFileError -> File::Error and PlatformFileInfo ->
File::Info

BUG=322664

Review URL: https://codereview.chromium.org/145303002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@247301 0039d316-1c4b-4281-b951-d872f2087c98
Fix some typos in Cloud Messaging documentation.

BUG=none

Review URL: https://codereview.chromium.org/146843004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@247302 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 247302