Bug 1065244 Part 1 - Add GetRectRelativeToFrame to nsLayoutUtils. f=mtseng, r=roc
Bug 1065244 Part 2 - Refactor event point on frame logic for SelectionCarets. f=mtseng, r=roc
Bug 1065244 Part 3 - Fix SelectionCarets::SelectWord() is hard to trigger. f=mtseng, r=roc

Fix this issue by deploying the same logic as selection carets in
TouchCaret::IsOnTouchCaret().