Handle jniresultcallback not loading due to lack of gms.Task.

[jonsimantov]

Description

Provide details of the change, and generalize the change in the PR title above.

app/src/util_android.h/.cc is a repository of many useful C++ functions to do Android/JNI things. Nearly every SDK we have calls util::Initialize() and util::Terminate() in its Android implementation, so that they can take advantage of the util_android functionality.

Unfortunately, although util_android mostly just utilizes basic Java and Android classes, there is one embedded class—JniResultCallback—that uses com.google.android.gms.Task, which is provided by com.google.android.gms:play-services-tasks.

This PR makes the initialization for JniResultHelper optional. If JniResultHelper failed to initialize, it will not be Terminated later.

Additionally, Firebase App was previously forcing the GoogleApiAvailability class to be initialized. Again, if play-services-base is not included, this will fail; this PR adds handling to gracefully ignore its failure, and (if the user tries to use ModuleInitializer without play-services-base included) return a detailed error.

This PR prevents apps that only use Firebase SDKs that don't use gms.Task under the hood—e.g. Analytics, Remote Config, Messaging—from crashing unless they include an explicit dependency on play-services-tasks (or play-services-base), because the class cannot be found.

This PR also adds a note to the readme about using the gradle dependency file, and adds the capability to include app without the play-services-base dependency, if the user wishes.

(Note, once this PR goes in, the gradle example added to the Readme should be modified from admob to gma.

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Testing

Describe how you've tested these changes. Link any manually triggered Integration tests or CPP binary SDK Packaging Github Action workflows, if applicable.

Integration test here was originally run with play-services-base not being included in any builds, to ensure it is never required. Since then, only Remote Config and AdMob have been modified to use appWithoutPlayServices.

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Type of Change

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• Bug fix. Add the issue # below if applicable.
• New feature. A non-breaking change which adds functionality.
• Other, such as a build process or documentation change.

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Notes

• Bug fixes and feature changes require an update to the Release Notes section of release_build_files/readme.md (see below).
• Read the contribution guidelines CONTRIBUTING.md.
• Changes to the public API require an internal API review. If you'd like to help us make Firebase APIs better, please propose your change in a feature request so that we can discuss it together.

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• General (Android): Added support for ______.
• Auth: Fixed a bug when ______.
• Database (iOS): Updated ______ support.
• Remote Config (Desktop): Fixed ______ on Windows.

Release notes should only be added for PRs that affect the packaged SDK. Please follow the above format as closely as possible. The release notes will be added to release_build_notes/readme.md upon merge, into the latest version (if not yet released) or Next Release.

[github-actions]

Integration test with FLAKINESS (succeeded after retry)

Requested by @jonsimantov on commit 6985af9
Last updated: Fri May 13 00:01 PDT 2022
View integration test log & download artifacts

Failures	Configs
auth	[TEST] [FLAKINESS] [iOS] [macos] [1/2 ios_device: ios_target] (1 failed tests)   FirebaseAuthTest.TestUpdateEmailAndPassword

Add flaky tests to go/fpl-cpp-flake-tracker