Mojo: Make a public test_support shared library.

mojo/mojo_public.gypi

 {
   'targets': [
     {
       'target_name': 'mojo_system',
       'type': 'shared_library',
       'defines': [
         'MOJO_SYSTEM_IMPLEMENTATION',
       ],
       'include_dirs': [
         '..',
@@ skipping 29 matching lines @@
       'direct_dependent_settings': {
         'include_dirs': [
           '..',
         ],
         'defines': [
           'GLES2_USE_MOJO',
         ],
       },
       'sources': [
         'public/gles2/gles2.h',
+        'public/gles2/gles2_export.h',
         'public/gles2/gles2_private.cc',
         'public/gles2/gles2_private.h',
-        'public/gles2/gles2_export.h',
       ],
     },
     {
+      'target_name': 'mojo_test_support',
+      'type': 'shared_library',
+      'defines': [
+        'MOJO_TEST_SUPPORT_IMPLEMENTATION',
+      ],
+      'include_dirs': [
+        '..',
+      ],
+      'direct_dependent_settings': {
+        'include_dirs': [
+          '..',
+        ],
+      },
+      'sources': [
+        'public/tests/test_support.h',
+        'public/tests/test_support_private.cc',
+        'public/tests/test_support_private.h',
+        'public/tests/test_support_export.h',
+      ],
+    },
+    {
       'target_name': 'mojo_public_test_utils',
       'type': 'static_library',
       'dependencies': [
         '../base/base.gyp:base',
         '../testing/gtest.gyp:gtest',
         'mojo_system',
+        'mojo_test_support',
       ],
       'sources': [
         'public/tests/test_utils.cc',
         'public/tests/test_utils.h',
       ],
     },
     {
       'target_name': 'mojo_public_bindings_unittests',
       'type': 'executable',
       'dependencies': [
@@ skipping 204 matching lines @@
         'public/shell/service.h',
       ],
       'includes': [ 'public/bindings/mojom_bindings_generator.gypi' ],
       'export_dependent_settings': [
         'mojo_bindings',
         'mojo_system',
       ],
     },
   ],
 }