Add gerrit_plugins gclient config

This change is needed to enable CQ for the tricium plugin.

Bug: 1201483
Change-Id: I685d04055a5cabd94c7f02a79a0b9cbc4694db0e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2847232
Reviewed-by: Josip Sokcevic <sokcevic@google.com>
Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
Commit-Queue: Gavin Mak <gavinmak@google.com>

recipes/README.recipes.md

@@ -1008,7 +1008,7 @@ Raises:
 
 [DEPS](/recipes/recipe_modules/gclient/examples/full.py#5): [gclient](#recipe_modules-gclient), [recipe\_engine/buildbucket][recipe_engine/recipe_modules/buildbucket], [recipe\_engine/context][recipe_engine/recipe_modules/context], [recipe\_engine/path][recipe_engine/recipe_modules/path], [recipe\_engine/properties][recipe_engine/recipe_modules/properties], [recipe\_engine/step][recipe_engine/recipe_modules/step]
 
-— **def [RunSteps](/recipes/recipe_modules/gclient/examples/full.py#53)(api):**
+— **def [RunSteps](/recipes/recipe_modules/gclient/examples/full.py#54)(api):**
 ### *recipes* / [gclient:tests/diff\_deps](/recipes/recipe_modules/gclient/tests/diff_deps.py)
 
 [DEPS](/recipes/recipe_modules/gclient/tests/diff_deps.py#7): [gclient](#recipe_modules-gclient), [recipe\_engine/assertions][recipe_engine/recipe_modules/assertions], [recipe\_engine/buildbucket][recipe_engine/recipe_modules/buildbucket], [recipe\_engine/path][recipe_engine/recipe_modules/path], [recipe\_engine/platform][recipe_engine/recipe_modules/platform], [recipe\_engine/properties][recipe_engine/recipe_modules/properties], [recipe\_engine/raw\_io][recipe_engine/recipe_modules/raw_io]

recipes/recipe_modules/gclient/config.py

@@ -444,3 +444,10 @@ def tint(c):
   soln.name = 'tint'
   soln.url = 'https://dawn.googlesource.com/tint.git'
   c.got_revision_mapping['tint'] = 'got_revision'
+
+@config_ctx()
+def gerrit_plugins(c):
+  s = c.solutions.add()
+  s.name = 'gerrit_plugins'
+  s.url = ChromiumGitURL(c, 'infra', 'gerrit-plugins', 'tricium.git')
+  c.got_revision_mapping['gerrit_plugins'] = 'got_revision'

recipes/recipe_modules/gclient/examples/full.py

@@ -26,6 +26,7 @@ TEST_CONFIGS = [
   'disable_syntax_validation',
   'emscripten_releases',
   'expect_tests',
+  'gerrit_plugins',
   'gerrit_test_cq_normal',
   'gyp',
   'infra',