net: boost AES-GCM ciphers if the machine has AES-NI.

We want to use ChaCha20 based cipher suites on machines that don't have AES-NI
and AES-GCM on those that do.

Note: this was https://codereview.chromium.org/75663004/ and the review took
place there. But codereview broke and I had to reupload as a different issue.

BUG=310768
R=wtc@chromium.org

Review URL: https://codereview.chromium.org/91913002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238113 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238113
Move ownership of URLRequestContextGetter out of DeviceManagementService

Change cloud policy code to use a profile-based request context when performing
user policy fetches. This requires moving the URLRequestContextGetter out of
the DeviceManagementService, so different clients can use different request
contexts.

BUG=322422,316115

Review URL: https://codereview.chromium.org/95223004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238114 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238114