new file mode 100644
--- /dev/null
+++ b/widget/xpwidgets/ActiveElementManager.cpp
@@ -0,0 +1,151 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "ActiveElementManager.h"
+#include "mozilla/EventStates.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/Services.h"
+#include "inIDOMUtils.h"
+#include "nsIDOMDocument.h"
+#include "nsIDOMElement.h"
+#include "nsIDOMEventTarget.h"
+#include "base/message_loop.h"
+#include "base/task.h"
+
+namespace mozilla {
+namespace widget {
+
+static int32_t sActivationDelayMs = 100;
+static bool sActivationDelayMsSet = false;
+
+ActiveElementManager::ActiveElementManager()
+  : mDomUtils(services::GetInDOMUtils()),
+    mCanBePan(false),
+    mCanBePanSet(false),
+    mSetActiveTask(nullptr)
+{
+  if (!sActivationDelayMsSet) {
+    Preferences::AddIntVarCache(&sActivationDelayMs,
+                                "ui.touch_activation.delay_ms",
+                                sActivationDelayMs);
+    sActivationDelayMsSet = true;
+  }
+}
+
+ActiveElementManager::~ActiveElementManager() {}
+
+void
+ActiveElementManager::SetTargetElement(nsIDOMEventTarget* aTarget)
+{
+  if (mTarget) {
+    // Multiple fingers on screen (since HandleTouchEnd clears mTarget).
+    ResetActive();
+    return;
+  }
+
+  mTarget = do_QueryInterface(aTarget);
+  TriggerElementActivation();
+}
+
+void
+ActiveElementManager::HandleTouchStart(bool aCanBePan)
+{
+  mCanBePan = aCanBePan;
+  mCanBePanSet = true;
+  TriggerElementActivation();
+}
+
+void
+ActiveElementManager::TriggerElementActivation()
+{
+  // Both HandleTouchStart() and SetTargetElement() call this. They can be
+  // called in either order. One will set mCanBePanSet, and the other, mTarget.
+  // We want to actually trigger the activation once both are set.
+  if (!(mTarget && mCanBePanSet)) {
+    return;
+  }
+
+  // If the touch cannot be a pan, make mTarget :active right away.
+  // Otherwise, wait a bit to see if the user will pan or not.
+  if (!mCanBePan) {
+    SetActive(mTarget);
+  } else {
+    mSetActiveTask = NewRunnableMethod(
+        this, &ActiveElementManager::SetActiveTask, mTarget);
+    MessageLoop::current()->PostDelayedTask(
+        FROM_HERE, mSetActiveTask, sActivationDelayMs);
+  }
+}
+
+void
+ActiveElementManager::HandlePanStart()
+{
+  // The user started to pan, so we don't want mTarget to be :active.
+  // Make it not :active, and clear any pending task to make it :active.
+  CancelTask();
+  ResetActive();
+}
+
+void
+ActiveElementManager::HandleTouchEnd(bool aWasClick)
+{
+  // If the touch was a click, make mTarget :active right away.
+  // nsEventStateManager will reset the active element when processing
+  // the mouse-down event generated by the click.
+  CancelTask();
+  if (aWasClick) {
+    SetActive(mTarget);
+  }
+
+  // Clear mTarget for next touch.
+  mTarget = nullptr;
+}
+
+void
+ActiveElementManager::SetActive(nsIDOMElement* aTarget)
+{
+  if (mDomUtils) {
+    mDomUtils->SetContentState(aTarget, NS_EVENT_STATE_ACTIVE.GetInternalValue());;
+  }
+}
+
+void
+ActiveElementManager::ResetActive()
+{
+  // Clear the :active flag from mTarget by setting it on the document root.
+  if (mTarget) {
+    nsCOMPtr<nsIDOMDocument> doc;
+    mTarget->GetOwnerDocument(getter_AddRefs(doc));
+    if (doc) {
+      nsCOMPtr<nsIDOMElement> root;
+      doc->GetDocumentElement(getter_AddRefs(root));
+      if (root) {
+        SetActive(root);
+      }
+    }
+  }
+}
+
+void
+ActiveElementManager::SetActiveTask(nsIDOMElement* aTarget)
+{
+  // This gets called from mSetActiveTask's Run() method. The message loop
+  // deletes the task right after running it, so we need to null out
+  // mSetActiveTask to make sure we're not left with a dangling pointer.
+  mSetActiveTask = nullptr;
+  SetActive(aTarget);
+}
+
+void
+ActiveElementManager::CancelTask()
+{
+  if (mSetActiveTask) {
+    mSetActiveTask->Cancel();
+    mSetActiveTask = nullptr;
+  }
+}
+
+}
+}
\ No newline at end of file

new file mode 100644
--- /dev/null
+++ b/widget/xpwidgets/ActiveElementManager.h
@@ -0,0 +1,85 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef __mozilla_widget_ActiveElementManager_h__
+#define __mozilla_widget_ActiveElementManager_h__
+
+#include "nsCOMPtr.h"
+#include "nsISupportsImpl.h"
+
+class inIDOMUtils;
+class nsIDOMEventTarget;
+class nsIDOMElement;
+class CancelableTask;
+
+namespace mozilla {
+namespace widget {
+
+/**
+ * Manages setting and clearing the ':active' CSS pseudostate in the presence
+ * of touch input.
+ */
+class ActiveElementManager {
+public:
+  NS_INLINE_DECL_REFCOUNTING(ActiveElementManager)
+
+  ActiveElementManager();
+  ~ActiveElementManager();
+
+  /**
+   * Specify the target of a touch. Typically this should be called right
+   * before HandleTouchStart(), but we give callers the flexibility to specify
+   * the target later if they don't know it at the time they call
+   * HandleTouchStart().
+   * |aTarget| may be nullptr.
+   */
+  void SetTargetElement(nsIDOMEventTarget* aTarget);
+  /**
+   * Handle a touch-start event.
+   * @param aCanBePan whether the touch can be a pan
+   */
+  void HandleTouchStart(bool aCanBePan);
+  /**
+   * Handle the start of panning.
+   */
+  void HandlePanStart();
+  /**
+   * Handle a touch-end or touch-cancel event.
+   * @param aWasClick whether the touch was a click
+   */
+  void HandleTouchEnd(bool aWasClick);
+private:
+  nsCOMPtr<inIDOMUtils> mDomUtils;
+  /**
+   * The target of the first touch point in the current touch block.
+   */
+  nsCOMPtr<nsIDOMElement> mTarget;
+  /**
+   * Whether the current touch block can be a pan. Set in HandleTouchStart().
+   */
+  bool mCanBePan;
+  /**
+   * Whether mCanBePan has been set for the current touch block.
+   * We need to keep track of this to allow HandleTouchStart() and
+   * SetTargetElement() to be called in either order.
+   */
+  bool mCanBePanSet;
+  /**
+   * A task for calling SetActive() after a timeout.
+   */
+  CancelableTask* mSetActiveTask;
+
+  // Helpers
+  void TriggerElementActivation();
+  void SetActive(nsIDOMElement* aTarget);
+  void ResetActive();
+  void SetActiveTask(nsIDOMElement* aTarget);
+  void CancelTask();
+};
+
+}
+}
+
+#endif /*__mozilla_widget_ActiveElementManager_h__ */

--- a/widget/xpwidgets/moz.build
+++ b/widget/xpwidgets/moz.build
@@ -1,23 +1,25 @@
 # -*- Mode: python; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 40 -*-
 # vim: set filetype=python:
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 EXPORTS += [
+    'ActiveElementManager.h',
     'APZCCallbackHelper.h',
     'ContentHelper.h',
     'GfxDriverInfo.h',
     'GfxInfoBase.h',
     'GfxInfoCollector.h',
 ]
 
 UNIFIED_SOURCES += [
+    'ActiveElementManager.cpp',
     'APZCCallbackHelper.cpp',
     'ContentHelper.cpp',
     'GfxDriverInfo.cpp',
     'GfxInfoBase.cpp',
     'GfxInfoCollector.cpp',
     'GfxInfoWebGL.cpp',
     'InputData.cpp',
     'nsBaseAppShell.cpp',