[chromium-reviews] Fix the bug: Scrolling the Spell-checker drop-down box adds add the languages...

Fix the bug: Scrolling the Spell-checker drop-down box adds the languages scrolled. Basically, when a spell check language changes, it is added to the accept languages list so that it is remembered later. However, when the list gets scrolled, it keeps adding all the languages it scrolled. So, I decided to fix this by adding only the latest language selected as the spell check dictionary language in the drop down.

Issue=8374

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=11022