[Regression] Do not trim spaces on edit preview or show changes

Since Ic05e5898 spaces are also trimmed on preview/show changes, which
is bad, because the autosummary "/* Header */ " gets trimmed and the
user text is direct written behind the slash. That is confusing and was
not so, before this change.

Force the trim on summary preview to have the right preview, because the
spaces are trimmed on save.

Change-Id: I0058ce31197f3ea8ffc5520f3f0f9e1bf6105066