Fix description of 'offsetY'of Layer in protocol.json
Fix description of 'offsetY'of Layer in protocol.json

BUG=None.

Review URL: https://codereview.chromium.org/372933002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@177647 bbb929c8-8fbe-4397-9dbb-9b2b20218538

primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs