Revert 159389 "Adding derived sources for platform."

> Adding derived sources for platform.
> 
> Pending moves from core/platform to platform have a dependency on
> derived sources. Add support in this changelist.
> 
> R=abarth@chromium.org, abarth, eseidel
> BUG=297477
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=159354
> 
> Review URL: https://codereview.chromium.org/26697002

TBR=schenney@chromium.org

Review URL: https://codereview.chromium.org/26908005

git-svn-id: svn://svn.chromium.org/blink/trunk@159392 bbb929c8-8fbe-4397-9dbb-9b2b20218538