mus: Add EventObserver to allow passively listening to UI events

components/mus/ws/event_tester.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_MUS_WS_EVENT_TESTER_H_
+#define COMPONENTS_MUS_WS_EVENT_TESTER_H_
+
+#include <stdint.h>
+
+#include "base/macros.h"
+#include "components/mus/public/interfaces/input_event_constants.mojom.h"
+#include "components/mus/public/interfaces/input_event_matcher.mojom.h"
+#include "components/mus/public/interfaces/input_key_codes.mojom.h"
+#include "ui/events/event.h"
+#include "ui/gfx/geometry/rect_f.h"
+
+namespace mus {
+namespace ws {
+
+// Wraps a mojom::EventMatcher and allows events to be tested against it.

[sky, 2016/04/21 17:23:03]

The reason we started putting the interfaces/structures declared in mojoms
inside the mojom namespace is so that you can use the same name. So, I would
name this EventMatcher.

[James Cook, 2016/04/22 18:22:54]

Done. There was a different file called event_matcher.h in
components/mus/public/cpp/, but that one just contains a single utility function
to build a mojom::EventMatcher. I renamed it to event_matcher_util.h because I
think have two event_matcher.h files is potentially confusing.

+class EventTester {
+ public:
+  explicit EventTester(const mojom::EventMatcher& matcher);
+  ~EventTester();
+
+  bool MatchesEvent(const ui::Event& event) const;
+
+  bool Equals(const EventTester& other) const;
+
+ private:
+  enum MatchFields {
+    NONE = 0,
+    TYPE = 1 << 0,
+    FLAGS = 1 << 1,
+    KEYBOARD_CODE = 1 << 2,
+    POINTER_KIND = 1 << 3,
+    POINTER_LOCATION = 1 << 4,
+  };
+
+  uint32_t fields_to_match_;
+  ui::EventType event_type_;
+  // Bitfields of kEventFlag* and kMouseEventFlag* values in
+  // input_event_constants.mojom.
+  int event_flags_;
+  int ignore_event_flags_;
+  uint16_t keyboard_code_;
+  ui::EventPointerType pointer_type_;
+  gfx::RectF pointer_region_;
+
+  DISALLOW_COPY_AND_ASSIGN(EventTester);
+};
+
+}  // namespace ws
+}  // namespace mus
+
+#endif  // COMPONENTS_MUS_WS_EVENT_TESTER_H_