Revert of Mojo: Eliminate duplicate C API symbols

mojo/mojo_variables.gypi

Index: mojo/mojo_variables.gypi
diff --git a/mojo/mojo_variables.gypi b/mojo/mojo_variables.gypi
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index 0000000000000000000000000000000000000000..e19aa95b2b7354166cf5c2ba63bb278fc70e60c0
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+++ b/mojo/mojo_variables.gypi
@@ -0,0 +1,50 @@
+# 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 various mojo .gyp files.
+#
+{
+  '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': "<(DEPTH)/mojo/mojo_edk.gyp:mojo_system_impl",
+        'mojo_system_for_loadable_module': "<(DEPTH)/mojo/mojo_edk.gyp:mojo_system_impl",
+      }, {
+        'mojo_system_for_component': "<(DEPTH)/mojo/mojo_public.gyp:mojo_system_placeholder",
+        'mojo_system_for_loadable_module': "<(DEPTH)/mojo/mojo_public.gyp:mojo_system",
+      }],
+    ],
+    'mojo_public_system_unittest_sources': [
+      '<(DEPTH)/mojo/public/c/system/tests/core_unittest.cc',
+      '<(DEPTH)/mojo/public/c/system/tests/core_unittest_pure_c.c',
+      '<(DEPTH)/mojo/public/c/system/tests/macros_unittest.cc',
+      '<(DEPTH)/mojo/public/cpp/system/tests/core_unittest.cc',
+      '<(DEPTH)/mojo/public/cpp/system/tests/watcher_unittest.cc',
+    ],
+  },
+}