Mojo: Add the ability to attach PlatformHandles to MessageInTransits.

mojo/system/message_in_transit.h

Index: mojo/system/message_in_transit.h
diff --git a/mojo/system/message_in_transit.h b/mojo/system/message_in_transit.h
index 966f84b0f9adde0ec04859f992a202d3cc7b5971..a4974cd3a13d43c3cbc28840a121a49034dd317a 100644
--- a/mojo/system/message_in_transit.h
+++ b/mojo/system/message_in_transit.h
@@ -11,6 +11,7 @@
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
+#include "mojo/embedder/platform_handle.h"
 #include "mojo/system/dispatcher.h"
 #include "mojo/system/system_impl_export.h"
 
@@ -211,7 +212,19 @@ class MOJO_SYSTEM_IMPL_EXPORT MessageInTransit {
 
   // Returns true if this message has dispatchers attached.
   bool has_dispatchers() const {
-    return dispatchers_.get() && !dispatchers_->empty();
+    return dispatchers_ && !dispatchers_->empty();
+  }
+
+  // Gets the platform-specific handles attached to this message; this may
+  // return null if there are none. Note that the caller may mutate the set of
+  // platform-specific handles.
+  std::vector<embedder::PlatformHandle>* platform_handles() {
+    return platform_handles_.get();
+  }
+
+  // Returns true if this message has platform-specific handles attached.
+  bool has_platform_handles() const {
+    return platform_handles_ && !platform_handles_->empty();
   }
 
   // Rounds |n| up to a multiple of |kMessageAlignment|.
@@ -278,6 +291,12 @@ class MOJO_SYSTEM_IMPL_EXPORT MessageInTransit {
   // some reason.)
   scoped_ptr<std::vector<scoped_refptr<Dispatcher> > > dispatchers_;
 
+  // Any platform-specific handles attached to this message (for inter-process
+  // transport). The vector (if any) owns the handles that it contains (and is
+  // responsible for closing them).
+  // TODO(vtl): With C++11, change it to a vector of |ScopedPlatformHandles|.
+  scoped_ptr<std::vector<embedder::PlatformHandle> > platform_handles_;
+
   DISALLOW_COPY_AND_ASSIGN(MessageInTransit);
 };