Add support for writing unit tests for Mojo-backed apps/extensions APIs.

extensions/extensions.gyp

Index: extensions/extensions.gyp
diff --git a/extensions/extensions.gyp b/extensions/extensions.gyp
index 43491832331309c4f024d1123a7e9ad46b9cde12..828ddfcea5ffae9dc0a30773d577aa8852a0022f 100644
--- a/extensions/extensions.gyp
+++ b/extensions/extensions.gyp
@@ -693,7 +693,14 @@
       'dependencies': [
         '../base/base.gyp:base',
         '../base/base.gyp:test_support_base',
+        '../content/content_resources.gyp:content_resources',
         '../content/content_shell_and_tests.gyp:test_support_content',
+        '../device/serial/serial.gyp:device_serial',
+        '../mojo/mojo.gyp:mojo_environment_chromium',
+        '../mojo/mojo.gyp:mojo_cpp_bindings',
+        '../mojo/mojo.gyp:mojo_js_bindings',
+        '../mojo/mojo.gyp:mojo_js_bindings_lib',
+        '../mojo/mojo.gyp:mojo_system_impl',
         '../testing/gmock.gyp:gmock',
         '../testing/gtest.gyp:gtest',
         'extensions_common',
@@ -710,6 +717,9 @@
         'common/one_shot_event_unittest.cc',
         'common/permissions/manifest_permission_set_unittest.cc',
         'common/user_script_unittest.cc',
+        'renderer/api_test_base.cc',
+        'renderer/api_test_base.h',
+        'renderer/api_test_base_unittest.cc',
         'renderer/event_unittest.cc',
         'renderer/json_schema_unittest.cc',
         'renderer/messaging_utils_unittest.cc',
@@ -731,6 +741,7 @@
           'action_name': 'repack_components_pack',
           'variables': {
             'pak_inputs': [
+              '<(SHARED_INTERMEDIATE_DIR)/content/content_resources.pak',
               '<(SHARED_INTERMEDIATE_DIR)/extensions/extensions_resources.pak',
               '<(SHARED_INTERMEDIATE_DIR)/extensions/extensions_renderer_resources.pak',
             ],