Add //mojo/edk/platform and move platform_task_runners.h there.

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 9408bd123f28222526789bde23866620645f3c66..0ae12490257053132451002fe728bc226eca2131 100644
--- a/mojo/edk/embedder/embedder.h
+++ b/mojo/edk/embedder/embedder.h
@@ -11,10 +11,10 @@
 
 #include "base/callback.h"
 #include "mojo/edk/embedder/channel_info_forward.h"
-#include "mojo/edk/embedder/platform_task_runner.h"
 #include "mojo/edk/embedder/process_type.h"
 #include "mojo/edk/embedder/scoped_platform_handle.h"
 #include "mojo/edk/embedder/slave_info.h"
+#include "mojo/edk/platform/task_runner.h"
 #include "mojo/public/cpp/system/message_pipe.h"
 
 namespace mojo {
@@ -89,9 +89,9 @@ MojoResult PassWrappedPlatformHandle(MojoHandle platform_handle_wrapper_handle,
 //     |platform_handle| is ignored (and should not be valid).
 void InitIPCSupport(
     ProcessType process_type,
-    util::RefPtr<PlatformTaskRunner>&& delegate_thread_task_runner,
+    util::RefPtr<platform::TaskRunner>&& delegate_thread_task_runner,
     ProcessDelegate* process_delegate,
-    util::RefPtr<PlatformTaskRunner>&& io_thread_task_runner,
+    util::RefPtr<platform::TaskRunner>&& io_thread_task_runner,
     ScopedPlatformHandle platform_handle);
 
 // Shuts down the subsystem initialized by |InitIPCSupport()|. This must be
@@ -132,7 +132,7 @@ ScopedMessagePipeHandle ConnectToSlave(
     SlaveInfo slave_info,
     ScopedPlatformHandle platform_handle,
     const base::Closure& did_connect_to_slave_callback,
-    util::RefPtr<PlatformTaskRunner>&& did_connect_to_slave_runner,
+    util::RefPtr<platform::TaskRunner>&& did_connect_to_slave_runner,
     std::string* platform_connection_id,
     ChannelInfo** channel_info);
 
@@ -150,7 +150,7 @@ ScopedMessagePipeHandle ConnectToSlave(
 ScopedMessagePipeHandle ConnectToMaster(
     const std::string& platform_connection_id,
     const base::Closure& did_connect_to_master_callback,
-    util::RefPtr<PlatformTaskRunner>&& did_connect_to_master_runner,
+    util::RefPtr<platform::TaskRunner>&& did_connect_to_master_runner,
     ChannelInfo** channel_info);
 
 // A "channel" is a connection on top of an OS "pipe", on top of which Mojo
@@ -209,7 +209,7 @@ ScopedMessagePipeHandle CreateChannelOnIOThread(
 ScopedMessagePipeHandle CreateChannel(
     ScopedPlatformHandle platform_handle,
     const base::Callback<void(ChannelInfo*)>& did_create_channel_callback,
-    util::RefPtr<PlatformTaskRunner>&& did_create_channel_runner);
+    util::RefPtr<platform::TaskRunner>&& did_create_channel_runner);
 
 // Destroys a channel that was created using |ConnectToMaster()|,
 // |ConnectToSlave()|, |CreateChannel()|, or |CreateChannelOnIOThread()|; must
@@ -225,7 +225,7 @@ void DestroyChannelOnIOThread(ChannelInfo* channel_info);
 void DestroyChannel(
     ChannelInfo* channel_info,
     const base::Closure& did_destroy_channel_callback,
-    util::RefPtr<PlatformTaskRunner>&& did_destroy_channel_runner);
+    util::RefPtr<platform::TaskRunner>&& did_destroy_channel_runner);
 
 // Inform the channel that it will soon be destroyed (doing so is optional).
 // This may be called from any thread, but the caller must ensure that this is