Mojo: (Theoretically) implement the read side of platform handle passing.

mojo/system/raw_channel.h

Index: mojo/system/raw_channel.h
diff --git a/mojo/system/raw_channel.h b/mojo/system/raw_channel.h
index 5eb9d0f04f257d2b4f7259f31bd15234ae1e0a71..8b4ef35f65fe980ce662ead805ebea85a7a4ffe4 100644
--- a/mojo/system/raw_channel.h
+++ b/mojo/system/raw_channel.h
@@ -12,6 +12,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/synchronization/lock.h"
+#include "mojo/embedder/platform_handle_vector.h"
 #include "mojo/embedder/scoped_platform_handle.h"
 #include "mojo/system/constants.h"
 #include "mojo/system/message_in_transit.h"
@@ -208,6 +209,15 @@ class MOJO_SYSTEM_IMPL_EXPORT RawChannel {
   // returns |IO_FAILED| or |IO_PENDING|.
   virtual IOResult ScheduleRead() = 0;
 
+  // Called by |OnReadCompleted()| to get the platform handles associated with
+  // the given platform handle table (from a message). This should only be
+  // called when |num_platform_handles| is nonzero. Returns null if the
+  // |num_platform_handles| handles are not available. Only called on the I/O
+  // thread (without |write_lock_| held).
+  virtual scoped_ptr<embedder::PlatformHandleVector> GetReadPlatformHandles(
+      size_t num_platform_handles,
+      const void* platform_handle_table) = 0;
+
   // Writes contents in |write_buffer_no_lock()|.
   // This class guarantees that:
   // - the |PlatformHandle|s given by |GetPlatformHandlesToSend()| and the