[Bug] Cannot add comment properly when comparing with a target branch.

[suguspnk]

Precondition/s:

1. Code review is ON.

Steps:

1. Compare current branch with a target branch.
2. Add a comment by clicking the + sign in the gutter.
3. While creating the comment, press arrow keys or any navigational keys or delete characters in the comment using backspace.

Expected: Caret will move in the comment area depending on the key pressed or if backspace was used, will delete a character in the comment area.

Actual: The caret in actual source file moves instead of inside the comment area and if backspace was used, the actual source file is edited instead of the comment area.