EDK: Remove MOJO_SYSTEM_IMPL_EXPORT, system_impl_export.h, etc.

mojo/edk/system/channel_manager.h

Index: mojo/edk/system/channel_manager.h
diff --git a/mojo/edk/system/channel_manager.h b/mojo/edk/system/channel_manager.h
index 342140fbdb9c2b00c06fa04508d7475548956524..dc2ca7e111c47e9026b047a72bf4c05fc334f134 100644
--- a/mojo/edk/system/channel_manager.h
+++ b/mojo/edk/system/channel_manager.h
@@ -36,7 +36,7 @@ class MessagePipeDispatcher;
 // This class manages and "owns" |Channel|s (which typically connect to other
 // processes) for a given process. This class is thread-safe, except as
 // specifically noted.
-class MOJO_SYSTEM_IMPL_EXPORT ChannelManager {
+class ChannelManager {
  public:
   // |io_thread_task_runner| should be the |TaskRunner| for the I/O thread, on
   // which this channel manager will create all channels. Connection manager is