Bug 1714680 - Implement `mach gtest --list-tests` r=ahal

Differential Revision: https://phabricator.services.mozilla.com/D116904

python/mozbuild/mozbuild/mach_commands.py

@@ -561,7 +561,13 @@ class GTestCommands(MachCommandBase):
         metavar="gtest_filter",
         help="test_filter is a ':'-separated list of wildcard patterns "
         "(called the positive patterns), optionally followed by a '-' "
-        "and another ':'-separated pattern list (called the negative patterns).",
+        "and another ':'-separated pattern list (called the negative patterns)."
+        "Test names are of the format SUITE.NAME. Use --list-tests to see all.",
+    )
+    @CommandArgument(
+        "--list-tests",
+        action="store_true",
+        help="list all available tests",
     )
     @CommandArgument(
         "--jobs",
@@ -655,6 +661,7 @@ class GTestCommands(MachCommandBase):
         shuffle,
         jobs,
         gtest_filter,
+        list_tests,
         tbpl_parser,
         enable_webrender,
         package,
@@ -730,6 +737,9 @@ class GTestCommands(MachCommandBase):
         if sys.platform.startswith("win") and "MOZ_LAUNCHER_PROCESS" in self.defines:
             args.append("--wait-for-browser")
 
+        if list_tests:
+            args.append("--gtest_list_tests")
+
         if debug or debugger or debugger_args:
             args = _prepend_debugger_args(args, debugger, debugger_args)
             if not args:
@@ -737,7 +747,7 @@ class GTestCommands(MachCommandBase):
 
         # Use GTest environment variable to control test execution
         # For details see:
-        # https://code.google.com/p/googletest/wiki/AdvancedGuide#Running_Test_Programs:_Advanced_Options
+        # https://google.github.io/googletest/advanced.html#running-test-programs-advanced-options
         gtest_env = {b"GTEST_FILTER": gtest_filter}
 
         # Note: we must normalize the path here so that gtest on Windows sees