Extract mojo_base.gyp from mojo.gyp

mojo/mojo_variables.gypi

+# Copyright 2014 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+#
+# A set of GYP variables that are shared between mojo.gyp and mojo_base.gyp
+#
+{
+  'variables': {
+    'chromium_code': 1,
+    'mojo_shell_debug_url%': "",
+    'conditions': [
+      #
+      # The following mojo_system-prefixed variables are used to express a
+      # dependency on the mojo system APIs.
+      #
+      # In a component == "shared_library" build, everything can link against
+      # mojo_system_impl because it is built as a shared library. However, in a
+      # component != "shared_library" build, mojo_system_impl is linked into an
+      # executable (e.g., mojo_shell), and must be injected into other shared
+      # libraries (i.e., Mojo Apps) that need the mojo system API.
+      #
+      # For component targets, add <(mojo_system_for_component) to your
+      # dependencies section.  For loadable module targets (e.g., a Mojo App),
+      # add <(mojo_system_for_loadable_module) to your dependencies section.
+      #
+      # NOTE: component != "shared_library" implies that we are generating a
+      # static library, and in that case, it is expected that the target
+      # listing the component as a dependency will specify either mojo_system
+      # or mojo_system_impl to link against. This enables multiple targets to
+      # link against the same component library without having to agree on
+      # which Mojo system library they are using.
+      #
+      ['component=="shared_library"', {
+        'mojo_system_for_component': "mojo_base.gyp:mojo_system_impl",
+        'mojo_system_for_loadable_module': "mojo_base.gyp:mojo_system_impl",
+      }, {
+        'mojo_system_for_component': "mojo_base.gyp:mojo_none",
+        'mojo_system_for_loadable_module': "mojo_base.gyp:mojo_system",
+      }],
+    ],
+  },
+}