importer: Some more cleanups to ImporterHost class.
importer: Some more cleanups to ImporterHost class.

- Remove unnecessary includes.
- Remove unnecessary forward declarations.
- Tweak some minor comments.

BUG=None
TEST=None

R=avi@chromium.org

Review URL: http://codereview.chromium.org/6712044

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@78790 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser