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

shell/task_runners.h

Index: shell/task_runners.h
diff --git a/shell/task_runners.h b/shell/task_runners.h
index f66024477d02d2b7c498c0b13e6c01f876a9d35a..5ed78b8b68c67262bcb02bad9e66506683e202f6 100644
--- a/shell/task_runners.h
+++ b/shell/task_runners.h
@@ -10,7 +10,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/single_thread_task_runner.h"
 #include "base/threading/thread.h"
-#include "mojo/edk/embedder/platform_task_runner.h"
+#include "mojo/edk/platform/task_runner.h"
 #include "mojo/edk/util/ref_ptr.h"
 
 namespace base {
@@ -27,13 +27,11 @@ class TaskRunners {
       const scoped_refptr<base::SingleThreadTaskRunner>& shell_runner);
   ~TaskRunners();
 
-  const mojo::util::RefPtr<mojo::embedder::PlatformTaskRunner>& shell_runner()
-      const {
+  const mojo::util::RefPtr<mojo::platform::TaskRunner>& shell_runner() const {
     return shell_runner_;
   }
 
-  const mojo::util::RefPtr<mojo::embedder::PlatformTaskRunner>& io_runner()
-      const {
+  const mojo::util::RefPtr<mojo::platform::TaskRunner>& io_runner() const {
     return io_runner_;
   }
 
@@ -42,9 +40,9 @@ class TaskRunners {
   }
 
  private:
-  mojo::util::RefPtr<mojo::embedder::PlatformTaskRunner> shell_runner_;
+  mojo::util::RefPtr<mojo::platform::TaskRunner> shell_runner_;
   scoped_ptr<base::Thread> io_thread_;
-  mojo::util::RefPtr<mojo::embedder::PlatformTaskRunner> io_runner_;
+  mojo::util::RefPtr<mojo::platform::TaskRunner> io_runner_;
 
   scoped_refptr<base::SequencedWorkerPool> blocking_pool_;