Set mime-type for html/css/js/gif in merge_into_svn.py
Set mime-type for html/css/js/gif in merge_into_svn.py

Created to fix https://code.google.com/p/skia/issues/detail?id=926 : doxygen docs are not browsable.
Review URL: https://codereview.appspot.com/6855094

git-svn-id: 32fc27f4dcfb6c0385cd9719852b95fe6680452d@6543 2bbb7eff-a529-9590-31e7-b0007b416f81

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,Tiger66639/skia-buildbot,Tiger66639/skia-buildbot,Tiger66639/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,Tiger66639/skia-buildbot,Tiger66639/skia-buildbot,Tiger66639/skia-buildbot,Tiger66639/skia-buildbot,google/skia-buildbot