Remove web/{android, gtk, win}

The {android, gtk, win} directories contain only WebInputEventFactory.cpp. We can just move these files to web/ with files renamed as WebInputEventFactoryAndroid.cpp,
WebInputEventFactoryGtk.cpp, WebInputEventFactoryWin.cpp respectively and remove the dir.
Moved the WebInputEventFactory.mm also to web/ but since web/mac/ still contains one more file, retained the dir. Probably can move the file also to web/ and remove the dir.

BUG=None

TEST=None;no behavior changes;

Review URL: https://codereview.chromium.org/27462002

git-svn-id: svn://svn.chromium.org/blink/trunk@159777 bbb929c8-8fbe-4397-9dbb-9b2b20218538