bookmarks: Only try to get favicon for URL nodes.
Rearrange the logic to simplify it. And do it in terms of node's type.
Also, it seems better to only call BookmarkModel's GetFavicon function on
BookmarkNode URLs as we don't set favicon for folders.
BUG=None
TEST=open chrome, bookmark some pages, create some folders, drag them
in-and-out around, no regressions should be observed.
R=sky@chromium.org
Review URL: https://codereview.chromium.org/763903003
Cr-Commit-Position: refs/heads/master@{#307276}
2 files changed
