Merge 33079 - Mac: give visual feedback for bookmark button drags....

Merge 33079 - Mac: give visual feedback for bookmark button drags.

Draw an "ugly black bar" (where "black" is actually a theme colour) to indicate
where a bookmark button that's being dragged will end up if dropped. This is a
stopgap measure for the beta. Later, we will make the buttons move around
instead (even if implementable in the time remaining, such animations would be a
crash risk).

BUG=17608
TEST=Drag bookmark bar buttons around. Make sure that the bar indicating where a button will be dropped is visible enough and accurate. Repeat with various themes.

Review URL: http://codereview.chromium.org/437051

TBR=viettrungluu@chromium.org

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=33105