Check chrome.runtime.lastError to fix error in chrome.runtime.lastError
Change registerFrameIfSizeAvailable to registerFrame, stop sending size

We were never using the area property, and it was causing an infinite
setTimeout loop on frames with height == 0 or width == 0 (often caused
by AdBlockPlus etc.).
Merge branch 'mrmr1993-stop-frame-register-infinite-loop'
Merge branch 'fix-insertCSS-error' of github.com:mrmr1993/vimium into mrmr1993-fix-insertCSS-error
Refactor CSS injection.
Merge branch 'mrmr1993-fix-insertCSS-error'
Fix detection of embedded objects.
Add mouseover and mouseout commands

Added LinkHints.activateModeToHover and LinkHints.unhoverLast to
perform hovering. These are unbound by default.

Also call LinkHints.unhoverLast automatically before hovering/
clicking the next link, to avoid permanently showing hover effects
(eg. IMDb watchlist grid view mode).