Make mojo_system static and mojo_system_impl a component, never use both

mojo/embedder/embedder_unittest.cc

Index: mojo/embedder/embedder_unittest.cc
diff --git a/mojo/embedder/embedder_unittest.cc b/mojo/embedder/embedder_unittest.cc
index be663fd92bca9117b44e19a49ce24d7a1d46b328..5ca8e1259641219316cdf1691ac718ecab711a0b 100644
--- a/mojo/embedder/embedder_unittest.cc
+++ b/mojo/embedder/embedder_unittest.cc
@@ -111,8 +111,6 @@ class EmbedderTest : public testing::Test {
 };
 
 TEST_F(EmbedderTest, ChannelsBasic) {
-  Init();
-
   {
     PlatformChannelPair channel_pair;
     ScopedTestChannel server_channel(test_io_thread()->task_runner(),
@@ -160,8 +158,6 @@ TEST_F(EmbedderTest, ChannelsBasic) {
 }
 
 TEST_F(EmbedderTest, ChannelsHandlePassing) {
-  Init();
-
   {
     PlatformChannelPair channel_pair;
     ScopedTestChannel server_channel(test_io_thread()->task_runner(),
@@ -295,7 +291,6 @@ TEST_F(EmbedderTest, ChannelsHandlePassing) {
 //  11.                                      (wait/cl.)
 //  12.                                                  (wait/cl.)
 TEST_F(EmbedderTest, MultiprocessChannels) {
-  Init();
   mojo::test::MultiprocessTestHelper multiprocess_test_helper;
   multiprocess_test_helper.StartChild("MultiprocessChannelsClient");
 
@@ -404,7 +399,6 @@ MOJO_MULTIPROCESS_TEST_CHILD_TEST(MultiprocessChannelsClient) {
 
   system::test::TestIOThread
       test_io_thread(system::test::TestIOThread::kAutoStart);
-  Init();
 
   {
     ScopedTestChannel client_channel(test_io_thread.task_runner(),