Include WebDevToolsMessageTransport.h in devtools_agent_filter.cc
Include WebDevToolsMessageTransport.h in devtools_agent_filter.cc

This is to allow cleaning up WebDevToolsAgentClient.h
(see https://bugs.webkit.org/show_bug.cgi?id=40914)

TEST=none
BUG=none

Review URL: http://codereview.chromium.org/2846024

git-svn-id: http://src.chromium.org/svn/trunk/src@50455 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: cd18fe2963f38eb42458f946c8839c7414ecdf44
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser