777 C*U with Autothrottle
If this pitch up maneuver were performed with the autothrottle engaged to hold speed, needed thrust would be applied (and continuously adjusted as required) to keep the target speed.
When the 777 was first introduced, this configuration of manual path control with the autothrottle engaged was not recommended. Operational experience, however, showed that the C*U system is quite good at balancing pitching moment disturbances from autothrottle engine adjustments. Now Boeing recommends using the autothrottle during manual path control.
An important thing to remember, however, is that with this combination of manual pitch control and autothrottle speed control there are actually two separate systems closing the loop on speed. C*U and the autothrottle are not in communication with each other so the speed targets within each are not identically matched. As a result, over a long period of time (many, many seconds to minutes depending on how close the two speed settings are) the airplane will end up in either an idle descent or a max power climb at the specified speed if left alone (no input on the column). The bottom line here is that autothrottle commanding speed with manual pitch control is not a substitute for autopilot.