Revert "Refactor code listening to platform events in content/renderer/."

content/public/renderer/platform_event_observer.h

-// Copyright 2014 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 CONTENT_PUBLIC_RENDERER_PLATFORM_EVENT_OBSERVER_H_
-#define CONTENT_PUBLIC_RENDERER_PLATFORM_EVENT_OBSERVER_H_
-
-#include "base/logging.h"
-#include "content/public/renderer/render_process_observer.h"
-#include "content/public/renderer/render_thread.h"
-
-namespace blink {
-class WebPlatformEventListener;
-}
-
-namespace content {
-
-// This class is used as a base class for PlatformEventObserver<ListenerType> to
-// allow storing PlatformEventObserver<> with different typename in the same
-// place.
-class PlatformEventObserverBase {
- public:
-  virtual ~PlatformEventObserverBase() { }
-
-  // Methods that need to be exposed in PlatformEventObserverBase. Their purpose
-  // is described in PlatformEventObserver<>.
-
-  virtual void Start(blink::WebPlatformEventListener* listener) = 0;
-  virtual void Stop() = 0;
-
-  // Helper method that allows an sub-class to write its own test helper.
-  // The |data| type MUST be known from the caller.
-  virtual void SendFakeDataForTesting(void* data) { }
-};
-
-// PlatformEventObserver<> defines the basic skeleton for an object requesting
-// the browser process to start/stop listening to some platform/hardware events
-// and observe the result.
-// The results are received via IPC, assuming that the object was correctly
-// registered as an observer via the constructor taking a RenderThread.
-template <typename ListenerType>
-class PlatformEventObserver : public PlatformEventObserverBase,
-                              public RenderProcessObserver {
- public:
-  // Creates a PlatformEventObserver that doesn't listen to responses from the
-  // browser process. Can be used for testing purposes or for observers that
-  // have other means to get their results.
-  PlatformEventObserver()
-      : is_observing_(false),
-        listener_(0) {
-  }
-
-  // Creates a PlatformEventObserver that registers to the RenderThread in order
-  // to intercept the received IPC messages (via OnControlMessageReceived). If
-  // |thread| is null, it will not register.
-  explicit PlatformEventObserver(RenderThread* thread)
-      : is_observing_(false),
-        listener_(0) {
-    if (thread)
-      thread->AddObserver(this);
-  }
-
-  // The observer will automatically stop observing when destroyed in case it
-  // did not stop before.
-  virtual ~PlatformEventObserver() {
-    if (is_observing())
-      Stop();
-  }
-
-  // Called when a new IPC message is received. Must be used to listen to the
-  // responses from the browser process if any expected.
-  virtual bool OnControlMessageReceived(const IPC::Message& msg) OVERRIDE {
-    return false;
-  }
-
-  // Start observing. Will request the browser process to start listening to the
-  // events. |listener| will receive any response from the browser process.
-  // Note: should not be called if already observing.
-  virtual void Start(blink::WebPlatformEventListener* listener) {
-    DCHECK(!is_observing());
-    listener_ = static_cast<ListenerType*>(listener);
-    is_observing_ = true;
-
-    SendStartMessage();
-  }
-
-  // Stop observing. Will let the browser know that it doesn't need to observe
-  // anymore.
-  virtual void Stop() {
-    DCHECK(is_observing());
-    listener_ = 0;
-    is_observing_ = false;
-
-    SendStopMessage();
-  }
-
- protected:
-  // This method is expected to send an IPC to the browser process to let it
-  // know that it should start observing.
-  // It is expected for subclasses to override it.
-  virtual void SendStartMessage() = 0;
-
-  // This method is expected to send an IPC to the browser process to let it
-  // know that it should start observing.
-  // It is expected for subclasses to override it.
-  virtual void SendStopMessage() = 0;
-
-  bool is_observing() const {
-    return is_observing_;
-  }
-
-  ListenerType* listener() {
-    return listener_;
-  }
-
- private:
-  bool is_observing_;
-  ListenerType* listener_;
-
-  DISALLOW_COPY_AND_ASSIGN(PlatformEventObserver);
-};
-
-} // namespace content
-
-#endif // CONTENT_PUBLIC_RENDERER_PLATFORM_EVENT_OBSERVER_H_