Revert of Mojo EDK: Introduce MojoQueryHandleSignalsState API

mojo/edk/system/handle_signals_state.h

Index: mojo/edk/system/handle_signals_state.h
diff --git a/mojo/edk/system/handle_signals_state.h b/mojo/edk/system/handle_signals_state.h
index f2412787cbf61ce31d1c8d16997d6981bb12c4e5..1c47a288c1e27914798e2f8395f2122b873a5172 100644
--- a/mojo/edk/system/handle_signals_state.h
+++ b/mojo/edk/system/handle_signals_state.h
@@ -5,9 +5,45 @@
 #ifndef MOJO_EDK_SYSTEM_HANDLE_SIGNALS_STATE_H_
 #define MOJO_EDK_SYSTEM_HANDLE_SIGNALS_STATE_H_
 
-#include "mojo/public/cpp/system/handle_signals_state.h"
+#include "mojo/edk/system/system_impl_export.h"
+#include "mojo/public/c/system/types.h"
 
-// TODO(rockot): Remove this header and use the C++ system library type
-// directly inside the EDK.
+namespace mojo {
+namespace edk {
+
+// Just "add" some constructors and methods to the C struct
+// |MojoHandleSignalsState| (for convenience). This should add no overhead.
+struct MOJO_SYSTEM_IMPL_EXPORT HandleSignalsState final
+    : public MojoHandleSignalsState {
+  HandleSignalsState() {
+    satisfied_signals = MOJO_HANDLE_SIGNAL_NONE;
+    satisfiable_signals = MOJO_HANDLE_SIGNAL_NONE;
+  }
+  HandleSignalsState(MojoHandleSignals satisfied,
+                     MojoHandleSignals satisfiable) {
+    satisfied_signals = satisfied;
+    satisfiable_signals = satisfiable;
+  }
+
+  bool equals(const HandleSignalsState& other) const {
+    return satisfied_signals == other.satisfied_signals &&
+           satisfiable_signals == other.satisfiable_signals;
+  }
+
+  bool satisfies(MojoHandleSignals signals) const {
+    return !!(satisfied_signals & signals);
+  }
+
+  bool can_satisfy(MojoHandleSignals signals) const {
+    return !!(satisfiable_signals & signals);
+  }
+
+  // (Copy and assignment allowed.)
+};
+static_assert(sizeof(HandleSignalsState) == sizeof(MojoHandleSignalsState),
+              "HandleSignalsState should add no overhead");
+
+}  // namespace edk
+}  // namespace mojo
 
 #endif  // MOJO_EDK_SYSTEM_HANDLE_SIGNALS_STATE_H_