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

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 8ea36c77010d8dbc171fc1e8ea833d436056b085..82f95b3fb698ef232cf546abb8919de0611a5b98 100644
--- a/mojo/edk/system/channel_manager.h
+++ b/mojo/edk/system/channel_manager.h
@@ -10,8 +10,8 @@
 #include <unordered_map>
 
 #include "base/callback_forward.h"
-#include "mojo/edk/embedder/platform_task_runner.h"
 #include "mojo/edk/embedder/scoped_platform_handle.h"
+#include "mojo/edk/platform/task_runner.h"
 #include "mojo/edk/system/channel_id.h"
 #include "mojo/edk/util/mutex.h"
 #include "mojo/edk/util/ref_ptr.h"
@@ -44,10 +44,9 @@ class ChannelManager {
   // which this channel manager will create all channels. Connection manager is
   // optional and may be null. All arguments (if non-null) must remain alive at
   // least until after shutdown completion.
-  ChannelManager(
-      embedder::PlatformSupport* platform_support,
-      util::RefPtr<embedder::PlatformTaskRunner>&& io_thread_task_runner,
-      ConnectionManager* connection_manager);
+  ChannelManager(embedder::PlatformSupport* platform_support,
+                 util::RefPtr<platform::TaskRunner>&& io_thread_task_runner,
+                 ConnectionManager* connection_manager);
   ~ChannelManager();
 
   // Shuts down the channel manager, including shutting down all channels (as if
@@ -66,7 +65,7 @@ class ChannelManager {
   // (in tests).
   void Shutdown(
       const base::Closure& callback,
-      util::RefPtr<embedder::PlatformTaskRunner>&& callback_thread_task_runner);
+      util::RefPtr<platform::TaskRunner>&& callback_thread_task_runner);
 
   // Creates a |Channel| and adds it to the set of channels managed by this
   // |ChannelManager|. This must be called from the I/O thread (given to the
@@ -93,7 +92,7 @@ class ChannelManager {
       ChannelId channel_id,
       embedder::ScopedPlatformHandle platform_handle,
       const base::Closure& callback,
-      util::RefPtr<embedder::PlatformTaskRunner>&& callback_thread_task_runner);
+      util::RefPtr<platform::TaskRunner>&& callback_thread_task_runner);
 
   // Gets the |Channel| with the given ID (which must exist).
   util::RefPtr<Channel> GetChannel(ChannelId channel_id) const;
@@ -118,7 +117,7 @@ class ChannelManager {
   void ShutdownChannel(
       ChannelId channel_id,
       const base::Closure& callback,
-      util::RefPtr<embedder::PlatformTaskRunner>&& callback_thread_task_runner);
+      util::RefPtr<platform::TaskRunner>&& callback_thread_task_runner);
 
   ConnectionManager* connection_manager() const { return connection_manager_; }
 
@@ -128,7 +127,7 @@ class ChannelManager {
   // that doesn't work with |base::Bind()|.
   void ShutdownHelper(
       const base::Closure& callback,
-      util::RefPtr<embedder::PlatformTaskRunner> callback_thread_task_runner);
+      util::RefPtr<platform::TaskRunner> callback_thread_task_runner);
 
   // Used by |CreateChannelOnIOThread()| and |CreateChannelHelper()|. Called on
   // the I/O thread. |bootstrap_channel_endpoint| is optional and may be null.
@@ -147,11 +146,11 @@ class ChannelManager {
       embedder::ScopedPlatformHandle platform_handle,
       util::RefPtr<ChannelEndpoint> bootstrap_channel_endpoint,
       const base::Closure& callback,
-      util::RefPtr<embedder::PlatformTaskRunner> callback_thread_task_runner);
+      util::RefPtr<platform::TaskRunner> callback_thread_task_runner);
 
   // Note: These must not be used after shutdown.
   embedder::PlatformSupport* const platform_support_;
-  const util::RefPtr<embedder::PlatformTaskRunner> io_thread_task_runner_;
+  const util::RefPtr<platform::TaskRunner> io_thread_task_runner_;
   ConnectionManager* const connection_manager_;
 
   // Note: |Channel| methods should not be called under |mutex_|.