CommandLine: add a CopySwitchesFrom() and AppendSwitchPath()

These are two common patterns in Chrome code: copying a
subset of switches from one CommandLine to another, and
appending a FilePath to a CommandLine.  This sets me up
to do a lot more deprecation in a follow-up change.

Review URL: http://codereview.chromium.org/3012021

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@54218 0039d316-1c4b-4281-b951-d872f2087c98
40 files changed