Revert of [mojo-edk] Simplify multiprocess pipe bootstrap

mojo/edk/embedder/embedder.h

Index: mojo/edk/embedder/embedder.h
diff --git a/mojo/edk/embedder/embedder.h b/mojo/edk/embedder/embedder.h
index 49b64c4c546ee82b86ed5a4cb2e9b7bb88f6d6a9..b43748ce154e668c0cc5b685172b1bcc1715faaf 100644
--- a/mojo/edk/embedder/embedder.h
+++ b/mojo/edk/embedder/embedder.h
@@ -118,12 +118,7 @@
 // |OnShutdownComplete()|.
 MOJO_SYSTEM_IMPL_EXPORT void ShutdownIPCSupport();
 
-// Creates a message pipe over an arbitrary platform channel. The other end of
-// the channel must also be passed to this function. Either endpoint can be in
-// any process.
-//
-// Note that the channel is only used to negotiate pipe connection, not as the
-// transport for messages on the pipe.
+// Unused. Crashes. Only here for linking.
 MOJO_SYSTEM_IMPL_EXPORT ScopedMessagePipeHandle
 CreateMessagePipe(ScopedPlatformHandle platform_handle);
 
@@ -133,10 +128,13 @@
 // either PreInitializeChildProcess() or SetParentPipe() must have been been
 // called at least once already.
 //
+// Note: This only exists for backwards compatibility with embedders that rely
+// on mojo::embedder::CreateChannel() behavior. If you have a means of passing
+// platform handles around, you can probably also pass strings around. If you
+// can pass strings around, use CreateParentMessagePipe() and
+// CreateChlidMessagePipe() instead (see below.)
+//
 // |callback| must be safe to call from any thread.
-//
-// DEPRECATED: Please don't use this. Use the synchronous version above. This
-// is now merely an inconvenient wrapper for that.
 MOJO_SYSTEM_IMPL_EXPORT void
 CreateMessagePipe(
     ScopedPlatformHandle platform_handle,
@@ -145,17 +143,8 @@
 // Creates a message pipe from a token. A child embedder must also have this
 // token and call CreateChildMessagePipe() with it in order for the pipe to get
 // connected.
-MOJO_SYSTEM_IMPL_EXPORT ScopedMessagePipeHandle
-CreateParentMessagePipe(const std::string& token);
-
-// Creates a message pipe from a token. A child embedder must also have this
-// token and call CreateChildMessagePipe() with it in order for the pipe to get
-// connected.
 //
 // |callback| must be safe to call from any thread.
-//
-// DEPRECATED: Please don't use this. Use the synchronous version above. This
-// is now merely an inconvenient wrapper for that.
 MOJO_SYSTEM_IMPL_EXPORT void
 CreateParentMessagePipe(
     const std::string& token,
@@ -164,17 +153,8 @@
 // Creates a message pipe from a token in a child process. The parent must also
 // have this token and call CreateParentMessagePipe() with it in order for the
 // pipe to get connected.
-MOJO_SYSTEM_IMPL_EXPORT ScopedMessagePipeHandle
-CreateChildMessagePipe(const std::string& token);
-
-// Creates a message pipe from a token in a child process. The parent must also
-// have this token and call CreateParentMessagePipe() with it in order for the
-// pipe to get connected.
 //
 // |callback| must be safe to call from any thread.
-//
-// DEPRECATED: Please don't use this. Use the synchronous version above. This
-// is now merely an inconvenient wrapper for that.
 MOJO_SYSTEM_IMPL_EXPORT void
 CreateChildMessagePipe(
     const std::string& token,