Reland "content: Copy plugin code from Blink to Chromium."

This relands r245843, which was reverted because it broke check_licenses
on Android Build. This time it was added the chromium copyright
boilerplate to files that had Apple copyright and replaced Google
copyright with Chromium one.

BUG=331302
TEST=None
R=boliu@chromium.org, jochen@chromium.org

Review URL: https://codereview.chromium.org/143373003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245954 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 245954