Remove default value checking in GN, adds getenv function, reorders parameters to rebase_path.

This allows us to have the default value vary according to other parameters. This is what we need in many cases, so having this restriction just made things more complicated.

The getenv function will allow us to replace some Python scripts with a fast native function call.

The use of rebase path is pretty annoying. 99% of all callers want the "from" directory to be the current one. I reordered the parameters to move the from directory later so we can have a default value for it.

This will require a patch to change all current callers of rebase_path when new deps are pulled.

BUG=342937
R=viettrungluu@chromium.org

Review URL: https://codereview.chromium.org/161783002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251821 0039d316-1c4b-4281-b951-d872f2087c98
Update RFHM tests to use only one test server and re-enable on Android.

BUG=187570
TEST=RenderFrameHostManagerTest.* passes on Android

Review URL: https://codereview.chromium.org/163753003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251822 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251821
SVN changes up to revision 251822
Hook up redirects for component builds

BUG=334379

Review URL: https://codereview.chromium.org/154463002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251823 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251823