Merge "SurfaceFlinger: Dispsync changePhaseOffset" into qt-r1-dev

                // new offset to allow for a seamless offset change without double-firing or

                // skipping.

                nsecs_t diff = oldPhase - phase;

                if (diff > mPeriod / 2) {

                    diff -= mPeriod;

                } else if (diff < -mPeriod / 2) {

                    diff += mPeriod;

                }

                if (phase < 0 && oldPhase > 0) {

                    diff += mPeriod;

                } else if (phase > 0 && oldPhase < 0) {

                    diff -= mPeriod;

                }

                eventListener.mLastEventTime -= diff;

                eventListener.mLastCallbackTime -= diff;

                mCond.signal();