Add a unique frame id and save it on HistoryItem.

Source/core/frame/Frame.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Simon Hausmann <hausmann@kde.org>
  *                     2000 Stefan Schimanski <1Stein@gmx.de>
  *                     2001 George Staikos <staikos@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2005 Alexey Proskuryakov <ap@nypop.com>
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
@@ skipping 82 matching lines @@
 }
 
 static inline float parentTextZoomFactor(Frame* frame)
 {
     Frame* parent = frame->tree().parent();
     if (!parent)
         return 1;
     return parent->textZoomFactor();
 }
 
+static int64_t nextFrameID()
+{
+    static int64_t next = static_cast<long long>(currentTime() * 10000000);
+    return ++next;
+}
+
 inline Frame::Frame(Page* page, HTMLFrameOwnerElement* ownerElement, FrameLoaderClient* frameLoaderClient)
     : m_page(page)
     , m_treeNode(this, parentFromOwnerElement(ownerElement))
     , m_loader(this, frameLoaderClient)
     , m_navigationScheduler(this)
     , m_ownerElement(ownerElement)
     , m_script(adoptPtr(new ScriptController(this)))
     , m_editor(Editor::create(*this))
     , m_spellChecker(SpellChecker::create(*this))
     , m_selection(adoptPtr(new FrameSelection(this)))
     , m_eventHandler(adoptPtr(new EventHandler(this)))
     , m_animationController(adoptPtr(new AnimationController(this)))
     , m_inputMethodController(InputMethodController::create(*this))
+    , m_id(nextFrameID())
     , m_pageZoomFactor(parentPageZoomFactor(this))
     , m_textZoomFactor(parentTextZoomFactor(this))
 #if ENABLE(ORIENTATION_EVENTS)
     , m_orientation(0)
 #endif
     , m_inViewSourceMode(false)
 {
     ASSERT(page);
 
     if (ownerElement) {
@@ skipping 551 matching lines @@
     if (!m_page)
         return 0;
 
     double ratio = m_page->deviceScaleFactor();
     if (RuntimeEnabledFeatures::devicePixelRatioIncludesZoomEnabled())
         ratio *= pageZoomFactor();
     return ratio;
 }
 
 } // namespace WebCore