Prevent app from accessing the GPU in the background in MultiFrameCodec

[ColdPaleLight]

Fix the issue : flutter/flutter#88353

Pre-launch Checklist

• I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
• I read the [Tree Hygiene] wiki page, which explains my responsibilities.
• I read and followed the [Flutter Style Guide] and the [C++, Objective-C, Java style guides].
• I listed at least one issue that this PR fixes in the description above.
• I added new tests to check the change I am making or feature I am adding, or Hixie said the PR is test-exempt. See [testing the engine] for instructions on
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• All existing and new tests are passing.

[gaaclarke]

Awesome, high quality PR, thanks. I just have a nit to factor out a helper function (feel free to pass if you are tight on time) also you just have to move the comment back where it was.

[gaaclarke]

This comment goes with the other MakeFromBitmap call.

[ColdPaleLight]

Done

[gaaclarke]

Nit: This pattern of synchronously executing a task happens multiple times in this test. I'd prefer that you pulled out a helper function so the test is easier to parse/maintain. Here's an example here:

engine/shell/common/engine_unittests.cc

Line 117 in 9c6c211

void PostUITaskSync(const std::function<void()>& function) {

[ColdPaleLight]

It's indeed a good idea. I will file a PR to do this later.

[gaaclarke]

FWIW this pattern happens so often in code (especially testing code) that I tried to add it to the TaskRunner API but was met with resistance under the fear that it would be misused. That's why I just made it a local method to the test suite.

[ColdPaleLight]

I filed a PR to do this: #28467