Generalize and refactor DeviceSensorEvent* architecture to support multi-event type targets.

Source/core/frame/DeviceEventDispatcherBase.cpp

+// 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.
+
+#include "config.h"
+#include "core/frame/DeviceEventDispatcherBase.h"
+
+#include "core/frame/DeviceEventControllerBase.h"
+#include "wtf/TemporaryChange.h"
+
+namespace WebCore {
+
+DeviceEventDispatcherBase::DeviceEventDispatcherBase()
+    : m_needsPurge(false)
+    , m_isDispatching(false)
+{
+}
+
+DeviceEventDispatcherBase::~DeviceEventDispatcherBase()
+{
+}
+
+void DeviceEventDispatcherBase::addController(DeviceEventControllerBase* controller)
+{
+    bool wasEmpty = m_controllers.isEmpty();
+    if (!m_controllers.contains(controller))
+        m_controllers.append(controller);
+    if (wasEmpty)
+        startListening();
+}
+
+void DeviceEventDispatcherBase::removeController(DeviceEventControllerBase* controller)
+{
+    // Do not actually remove the controller from the vector, instead zero them out.
+    // The zeros are removed in these two cases:
+    // 1. either immediately if we are not dispatching any events,
+    // 2. or after events to all controllers have dispatched (see notifyControllers()).
+    // This is to correctly handle the re-entrancy case when a controller is destroyed
+    // while the events are still being dispatched.
+    size_t index = m_controllers.find(controller);
+    if (index == kNotFound)
+        return;
+
+    m_controllers[index] = 0;
+    m_needsPurge = true;
+
+    if (!m_isDispatching)
+        purgeControllers();
+}
+
+void DeviceEventDispatcherBase::purgeControllers()
+{
+    ASSERT(m_needsPurge);
+
+    size_t i = 0;
+    while (i < m_controllers.size()) {
+        if (!m_controllers[i]) {
+            m_controllers[i] = m_controllers.last();
+            m_controllers.removeLast();
+        } else {
+            ++i;
+        }
+    }
+
+    m_needsPurge = false;
+
+    if (m_controllers.isEmpty())
+        stopListening();
+}
+
+void DeviceEventDispatcherBase::notifyControllers()
+{
+    {
+        TemporaryChange<bool> changeIsDispatching(m_isDispatching, true);
+        // Don't notify controllers removed or added during event dispatch.
+        size_t size = m_controllers.size();
+        for (size_t i = 0; i < size; ++i) {
+            if (m_controllers[i])
+                m_controllers[i]->didUpdateData();
+        }
+    }
+
+    if (m_needsPurge)
+        purgeControllers();
+}
+
+} // namespace WebCore