Linux flutter_gallery__memory_nav is 2.60% flaky

[flutterflakybot]

The post-submit test builder Linux flutter_gallery__memory_nav had a flaky ratio 2.60% for the past 15 days, which is above our 2.00% threshold.

One recent flaky example for a same commit: https://ci.chromium.org/ui/p/flutter/builders/prod/Linux%20flutter_gallery__memory_nav/2136
Commit: flutter@ed6c932
Flaky builds:
https://ci.chromium.org/ui/p/flutter/builders/prod/Linux%20flutter_gallery__memory_nav/2136
https://ci.chromium.org/ui/p/flutter/builders/prod/Linux%20flutter_gallery__memory_nav/2101

Succeeded builds (3 most recent):
https://ci.chromium.org/ui/p/flutter/builders/prod/Linux%20flutter_gallery__memory_nav/2140
https://ci.chromium.org/ui/p/flutter/builders/prod/Linux%20flutter_gallery__memory_nav/2139
https://ci.chromium.org/ui/p/flutter/builders/prod/Linux%20flutter_gallery__memory_nav/2138

Please follow https://github.com/flutter/flutter/wiki/Reducing-Test-Flakiness#fixing-flaky-tests to fix the flakiness and enable the test back after validating the fix (internal dashboard to validate: go/flutter_test_flakiness).