Add IGNORE_DEPS_CHANGES flag and coverage builder.

scripts/slave/recipe_modules/chromium_tests/chromium_chromiumos.py

Index: scripts/slave/recipe_modules/chromium_tests/chromium_chromiumos.py
diff --git a/scripts/slave/recipe_modules/chromium_tests/chromium_chromiumos.py b/scripts/slave/recipe_modules/chromium_tests/chromium_chromiumos.py
index c321966baa8570001bd7ef826e338fd0d33b5f74..7a7dfc426dbf0acaaae457c4570849ebbad8606e 100644
--- a/scripts/slave/recipe_modules/chromium_tests/chromium_chromiumos.py
+++ b/scripts/slave/recipe_modules/chromium_tests/chromium_chromiumos.py
@@ -170,6 +170,24 @@ SPEC = {
       },
       'enable_swarming': True,
     },
+
+    # Add a coverage builder to exercise configs that are leveraged in other
+    # recipe collections to build chrome packages:
+    # - "ignore_deps_changes"
+    'Package Builder (Coverage)': {
+      'chromium_config': 'chromium',
+      'chromium_apply_config': ['chromeos', 'ninja_confirm_noop',
+                                'ignore_deps_changes', 'mb'],
+      'gclient_config': 'chromium',
+      'chromium_config_kwargs': {
+        'BUILD_CONFIG': 'Debug',
+        'TARGET_BITS': 64,
+      },
+      'bot_type': 'builder',
+      'testing': {
+        'platform': 'linux',
+      },
+    },
   },
 }