Add a basic Mojo app that initializes V8

mojo/mojo.gyp

Index: mojo/mojo.gyp
diff --git a/mojo/mojo.gyp b/mojo/mojo.gyp
index 3ffdf7418a738985d4bea78b50b9e1d0cbce7dfe..72e6477a521f07a7457cd8365cf9bcd4e12551e2 100644
--- a/mojo/mojo.gyp
+++ b/mojo/mojo.gyp
@@ -21,6 +21,7 @@
         'mojo_shell_lib',
         'mojo_shell',
         'mojo_utility',
+        'mojo_js',
         'sample_app',
         'mojo_bindings',
         'mojo_bindings_test',
@@ -269,6 +270,21 @@
       ],
     },
     {
+      'target_name': 'mojo_js',
+      'type': 'shared_library',
+      'include_dirs': [
+        '..'
+      ],
+      'dependencies': [
+        '../v8/tools/gyp/v8.gyp:v8',
+      ],
+      'sources': [
+        'apps/js/main.cc',
+        'apps/js/v8_environment.cc',
+        'apps/js/v8_environment.h',
+      ],
+    },
+    {
       'target_name': 'sample_app',
       'type': 'shared_library',
       'dependencies': [