Flutter DevTools Performance FPS is not correct

##### At the same time

##### Here is Android Studio frame info 51.2 fps

##### Here is web DevTools frame info 60 fps


On my mobile phone side，it's has Jank, so i think the web Flutter DevTools Performances is not correct ~

Flutter doctor

Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 2.0.3, on macOS 11.2.3 20D91 darwin-x64, locale zh-Hans-CN)
[!] Android toolchain - develop for Android devices (Android SDK version 30.0.3)
! Some Android licenses not accepted. To resolve this, run: flutter doctor --android-licenses
[✓] Xcode - develop for iOS and macOS
[✓] Chrome - develop for the web
[✓] Android Studio (version 4.1)
[✓] VS Code (version 1.54.1)
[✓] Connected device (2 available)

! Doctor found issues in 1 category.

Start by reproducing the reported comparison using the Flutter 2.0.3 setup described, checking Android Studio's frame information against the web DevTools Performance view. The issue is done when the FPS and jank measurements are shown to be consistent or the discrepancy is clearly explained and corrected.

Scritto dal modello di indicizzazione a partire dal testo della issue.