Fixed dragging a folder from bookmark manager to open all elements in new tabs

Dropping a bookmark folder on Omnibox or Tab strip will open all of the urls in
separate tabs.

Note that this does not include urls within nested folders, because
BookmarkNodeData.WriteToClipboard (bookmark_node_data.cc:190) does not put urls
from nested folders into clipboard.

I have two questions from reviewers:

1) Do we have to record metrics in ToolbarController like what we have in
TabStripController.OpenUrl()?

2) I could not find any unit test for testing DropUrls of tab_strip_controller.mm
and toolbar_controller.mm, am I right?

BUG=661765

Review-Url: https://codereview.chromium.org/2502483002
Cr-Commit-Position: refs/heads/master@{#434124}
2 files changed