cobalt/shell: Add Content Browser Tests

[Awallky]

This adds the minimum framework for content browser tests to be run on cobalt's content_shell_lib and content_shell_app. This adds only the content_main_runner_impl_browsertest and navigation_browsertest test suites, with most of the test sources from content/shell:content_browsertests omitted to reduce this PR's complexity.
It is a direct copy of the libraries under //content/test needed for content_browsertests.

Note: Overall, this should not affect the behavior or size of libcobalt or cobalt/shell. All of the copies are for testing and so that there are no dependencies upon content/shell.

Below is a detailed description and reasoning behind each change:

• //BUILD.gn: Enables targets under cobalt/testing to be recognized and built
• //build/android/pylib/gtest/gtest_test_instance.py - Needed for the cobalt tests to be recognized and properly run by the test runners.
• //cobalt/shell/BUILD.gn:
  * Added a new android_shell_descriptors source set.
  * Made content_shell_lib_deps and content_shell_app_deps visible to //cobalt/testing/*.
  * Added a pak target to repack resources.
  • //cobalt/shell/android/BUILD.gn - Enables the cobat/shell to be built and packaged into a test library for use by the test runners
  • //cobalt/testing/browser_tests/BUILD.gn: This is a new file that defines the cobalt_browsertests target and its dependencies.
  • //content/public/test/android/javatests/src/org/chromium/content_public/browser/test/mock/MockWebContents.java: Added onResume and onFreeze methods, since builds failed without them.
  • //cobalt/shell/android/browsertests/src/org/chromium/content_shell/browsertests/* - Classes copied over from the same content/shell directory for testing use.
  • content/app/BUILD.gn, content/browser/BUILD.gn, content/child/BUILD.gn, content/common/BUILD.gn, content/gpu/BUILD.gn, content/renderer/BUILD.gn, content/utility/BUILD.gn, content/services/auction_worklet/public/mojom/BUILD.gn, media/mojo/clients/BUILD.gn, third_party/blink/public/common/BUILD.gn: Added //cobalt/testing/* to the visibility of various targets.

Future additions can include the content_unittests built on cobalt-specific changes and to include more tests in content browser tests that provide more coverage of the library.

Note: Not all tests pass. See test results - http://shortn/_dGJDarcvJY.

Test: out/android-arm_devel/bin/run_cobalt_browsertests -v
Fixed: 425936227

[Awallky]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces a comprehensive framework for content browser tests, which is a significant step forward for our testing capabilities. The changes are extensive, primarily involving the addition of new files and build configurations to support the test environment on Android.

My review identified a few areas needing attention:

• Critical: There are a couple of incorrect fully-qualified class names in Android layout XML files that will cause runtime crashes.
• High: Several new C++ header files use incorrect include guards, which could lead to compilation issues. This seems to be a result of copy-pasting files without updating them for their new location.

Addressing these points will improve the correctness and maintainability of this new test framework. Great work on this large and important feature.

[Awallky]

/gemini review

[gemini-code-assist]

Code Review

This pull request successfully adds the foundational framework for content browser tests in Cobalt, a crucial step for improving test coverage and decoupling from content/shell. The changes are extensive, involving numerous new files and build system modifications, which appear to be correctly adapted from their Chromium counterparts.

I've identified a few areas for improvement, including a critical memory leak in the test fixture, some uses of deprecated Android APIs, and minor opportunities to align with best practices for code maintainability and accessibility. Addressing these points will help ensure the new test framework is robust and easy to maintain.

[haozheng-cobalt]

Looks good in general to me.
Just 2 main nit issues:

1. We should update all copyrights to Cobalt.
2. and wrap Cobalt's logic in if(is_cobalt) for BUILD files in the upstream directories.