DevTools: Use CodeMirror modes instead of highlight tokenizers

This patch completely removes our generated tokenizers in favor of
CodeMirror modes. 
Removal of TextEditorModel (which is already not used for some time) happens in this patch as well as it produces compilation warnings caused by lack of tokenizers.

BUG=260589

Review URL: https://chromiumcodereview.appspot.com/22638008

git-svn-id: svn://svn.chromium.org/blink/trunk@156210 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Improve 'SpeechRecognition.start' exception message.

BUG=270033

Review URL: https://chromiumcodereview.appspot.com/22811004

git-svn-id: svn://svn.chromium.org/blink/trunk@156211 bbb929c8-8fbe-4397-9dbb-9b2b20218538