Link to touchpad pinch zoom design doc in README

Bug: 787924
Change-Id: I4da50acf43aa180cd62ea5e2210c5d54adda1dcf
Reviewed-on: https://chromium-review.googlesource.com/1140673
Reviewed-by: Dave Tapuska <dtapuska@chromium.org>
Commit-Queue: Kevin McNee <mcnee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575708}
1 file changed