[usecase-webapi] Improve PerformanceTimeline usecase

- Adjust the case with screen view

Impacted tests(approved): new 0, update 1, delete 0
Unit test platform: [Android]
Unit test result summary: pass 1, fail 0, block 0
I could not understand this purpose, and the last phrase has grammar error. should be "the time of loading image on the page it takes" than add "is correct/ is longer than 0 seconds...(should follow your purpose)"