Mojo EDK: Introduce MojoQueryHandleSignalsState API

mojo/public/cpp/system/handle.h

Index: mojo/public/cpp/system/handle.h
diff --git a/mojo/public/cpp/system/handle.h b/mojo/public/cpp/system/handle.h
index 5b2eb7bb1d8b61a34a651ba7a8521e620bd08762..3f949e73090395dc3d54483b5a6fc3bf691897a9 100644
--- a/mojo/public/cpp/system/handle.h
+++ b/mojo/public/cpp/system/handle.h
@@ -13,6 +13,7 @@
 #include "base/macros.h"
 #include "mojo/public/c/system/functions.h"
 #include "mojo/public/c/system/types.h"
+#include "mojo/public/cpp/system/handle_signals_state.h"
 
 namespace mojo {
 
@@ -170,6 +171,14 @@ class Handle {
     DCHECK_EQ(MOJO_RESULT_OK, result);
   }
 
+  HandleSignalsState QuerySignalsState() const {
+    HandleSignalsState signals_state;
+    MojoResult result = MojoQueryHandleSignalsState(
+        value_, static_cast<MojoHandleSignalsState*>(&signals_state));
+    DCHECK_EQ(MOJO_RESULT_OK, result);
+    return signals_state;
+  }
+
  private:
   MojoHandle value_;