Linux flutter_gallery__image_cache_memory is 1.37% flaky

[flutterflakybot]

The post-submit test builder Linux flutter_gallery__image_cache_memory had a flaky ratio 1.37% for the past 15 days, which is the flakist test below 2.00% threshold.

One recent flaky example for a same commit: https://ci.chromium.org/ui/p/flutter/builders/prod/Linux%20flutter_gallery__image_cache_memory/2026
Commit: flutter@f46cfa0
Failed build:
https://ci.chromium.org/ui/p/flutter/builders/prod/Linux%20flutter_gallery__image_cache_memory/2033
https://ci.chromium.org/ui/p/flutter/builders/prod/Linux%20flutter_gallery__image_cache_memory/2026

Succeeded build (3 most recent):
https://ci.chromium.org/ui/p/flutter/builders/prod/Linux%20flutter_gallery__image_cache_memory/2053
https://ci.chromium.org/ui/p/flutter/builders/prod/Linux%20flutter_gallery__image_cache_memory/2051
https://ci.chromium.org/ui/p/flutter/builders/prod/Linux%20flutter_gallery__image_cache_memory/2050

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).