Complete removing Blink gyp files.

Move the remaining modules sources into subdirectories.

Update the toplevel .gn file to remove all the now-obsolete references to gypi_to_gn.py exec_script calls.

R=dpranke@chromium.org

Review-Url: https://codereview.chromium.org/2323393004
Cr-Original-Commit-Position: refs/heads/master@{#417760}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: de7b265816adaad444e1dbdfe306d2a16539d9cd