This reverts commit 99d8d3c21f.
We need to revert the CodeMirror upgrade to 5.11 which was done by
Id02e65 because it broke displaying the file diff for certain files as
reported by issue 3927 [1]. Since this commit relies on the new
CodeMirror version is must be reverted as well.
[1] https://code.google.com/p/gerrit/issues/detail?id=3927
Change-Id: I6b15aa239666348e5c4ac50f4b248ef9a8f00cc5
81b830df4e