[shaders] Make CodeMirror resizeable.
[shaders] Make CodeMirror resizeable.

Bug: skia:11272
Change-Id: I0a9bee405c9d01e4118d373ea7ce1e013089eb98
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/377953
Reviewed-by: Joe Gregorio <b9cf2471ff6d33504cafe8e6f356b732b2cadced@google.com>

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