virtual/not-site-per-process

Summary

Layout tests use the default site isolation from the platform they are run on. For example, strict site isolation (aka site-per-process) is used on desktop platforms.

Additionally, on platforms where strict site isolation is enabled, layout tests opt into slightly stricter isolation and enabling isolating same-site origins used by Web Platform Tests. This ensures that features covered by WPT also provide sufficient coverage of how these feature behave in presence of out-of-process iframes.

Tests under virtual/not-site-per-process (defined in VirtualTestSuites) are run with --disable-site-isolation-trials cmdline flag which turns off site isolation. This is needed to preserve test coverage provided by around 60 tests that fail when run with site isolation.

Instead of including http/tests/devtools/isolated-code-cache tests here, we split into two virtual test suites virtual/not-split-http-cache-not-site-per-process and virtual/split-http-cache-not-site-per-process, which disable and enable HTTP cache partitioning, respectively. This split is needed as a test checks whether cross-origin resources were cached.

Tests incompatible with WPT origin isolation

Tests that modify document.domain are incompatible with isolation of WPT origins. The tests need to stay under virtual/not-site-per-process forever. See exclusive_tests in not-site-per-process section in VirtualTestSuites.

Tests that need further investigation and/or decisions

Remaining tests need further investigation as they may either 1) hide previously unknown OOPIF-related bugs or 2) expose known OOPIF-related differences in product behavior or 3) expose known OOPIF-support issues in tests or in the test harness. Over time, such tests should be removed from virtual/not-site-per-process. These tests are covered by web_tests/TestExpectations file.