Night mode CSS is buggy when horizontal scroll is needed for open-source version. about tie

[DubeySandeep]

Hi @kchen05, I was investigating around this issue and found it's reproducible even if you will press "tab" key just after changing the theme.

I found that with tab key press or on clicking on the scroll bar the Codemirror get focused (you can see a borderline) and the CodeMirror gets into the accessible mode, whereas when we are changing the theme we are only changing the codeMirrorOptions.theme

tie/client/question/components/LearnerViewDirective.js

Lines 1064 to 1070 in 52160a2

	$scope.changeTheme = function(newThemeName) {
	$scope.pulseAnimationEnabled = false;
	if (newThemeName === THEME_NAME_DARK) {
	$scope.codeMirrorOptions.theme = 'mbo';
	} else {
	$scope.codeMirrorOptions.theme = 'default';
	}

We should also change the $scope.accessibleCodeMirrorOptions.theme.
Currently, I'm not pretty aware of "accessibleMode" so I don't know whether it's an expected behavior or not (clicking on scroll bar should make the Codemirror into accessible mode). If it's an expected behavior then I'll send a PR! :)

One more issue I found:
On changing theme the scrollbar style remains the same till you click on it.