EDK: Add PlatformHandleWatcher to Channel (and ChannelManager) classes.

mojo/edk/system/channel_test_base.cc

Index: mojo/edk/system/channel_test_base.cc
diff --git a/mojo/edk/system/channel_test_base.cc b/mojo/edk/system/channel_test_base.cc
index ecbf783ce176ac7f089434ae8123951cd0018c49..cc35b634391510c28f1ff578106b0fcb5431e876 100644
--- a/mojo/edk/system/channel_test_base.cc
+++ b/mojo/edk/system/channel_test_base.cc
@@ -38,7 +38,9 @@ void ChannelTestBase::InitChannelOnIOThread(unsigned i) {
 
   CHECK(raw_channels_[i]);
   CHECK(channels_[i]);
-  channels_[i]->Init(std::move(raw_channels_[i]));
+  channels_[i]->Init(io_thread()->task_runner().Clone(),
+                     io_thread()->platform_handle_watcher(),
+                     std::move(raw_channels_[i]));
 }
 
 void ChannelTestBase::CreateAndInitChannelOnIOThread(unsigned i) {