Added pinch viewport offset to history item.

Source/core/frame/PinchViewport.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 46 matching lines @@
 using blink::WebScrollbar;
 using blink::WebScrollbarLayer;
 using WebCore::FrameHost;
 using WebCore::GraphicsLayer;
 using WebCore::GraphicsLayerFactory;
 
 namespace WebCore {
 
 PinchViewport::PinchViewport(FrameHost& owner)
     : m_frameHost(owner)
-    , m_scale(1)
 {
+    reset();
 }
 
 PinchViewport::~PinchViewport() { }
 
 void PinchViewport::setSize(const IntSize& size)
 {
     ASSERT(mainFrame() && mainFrame()->view());
 
     if (!m_innerViewportContainerLayer || !m_innerViewportScrollLayer)
         return;
 
     if (m_size == size)
         return;
 
     m_size = size;
     m_innerViewportContainerLayer->setSize(m_size);
 
     // Make sure we clamp the offset to within the new bounds.
     setLocation(m_offset);
 
     // Need to re-compute sizes for the overlay scrollbars.
     setupScrollbar(WebScrollbar::Horizontal);
     setupScrollbar(WebScrollbar::Vertical);
 }
 
+void PinchViewport::reset()
+{
+    setLocation(FloatPoint());
+    setScale(1);
+}
+
 void PinchViewport::mainFrameDidChangeSize()
 {
     // In unit tests we may not have initialized the layer tree.
     if (m_innerViewportScrollLayer)
         m_innerViewportScrollLayer->setSize(contentsSize());
 
     // Make sure the viewport's offset is clamped within the newly sized main frame.
     setLocation(m_offset);
 }
 
 FloatRect PinchViewport::visibleRect() const
 {
     FloatSize scaledSize(m_size);
     scaledSize.scale(1 / m_scale);
     return FloatRect(m_offset, scaledSize);
 }
 
 void PinchViewport::setLocation(const FloatPoint& newLocation)
 {
     FloatPoint clampedOffset(clampOffsetToBoundaries(newLocation));
 
     if (clampedOffset == m_offset)
         return;
 
     m_offset = clampedOffset;
 
     ScrollingCoordinator* coordinator = m_frameHost.page().scrollingCoordinator();
     ASSERT(coordinator);
     coordinator->scrollableAreaScrollLayerDidChange(this);
+
+    mainFrame()->loader().saveScrollState();
 }
 
 void PinchViewport::setScale(float scale)
 {
+    if (scale == m_scale)
+        return;
+
     m_scale = scale;
 
+    if (mainFrame())
+        mainFrame()->loader().saveScrollState();
+
     // Old-style pinch sets scale here but we shouldn't call into the
     // clamping code below.
     if (!m_innerViewportScrollLayer)
         return;
 
     // Ensure we clamp so we remain within the bounds.
     setLocation(visibleRect().location());
+
+    // TODO: We should probably be calling scaleDidChange type functions here.
+    // see Page::setPageScaleFactor.
 }
 
 // Modifies the top of the graphics layer tree to add layers needed to support
 // the inner/outer viewport fixed-position model for pinch zoom. When finished,
 // the tree will look like this (with * denoting added layers):
 //
 // *innerViewportContainerLayer (fixed pos container)
 //  +- *pageScaleLayer
 //  |   +- *innerViewportScrollLayer
 //  |       +-- overflowControlsHostLayer (root layer)
@@ skipping 235 matching lines @@
     } else if (graphicsLayer == m_overlayScrollbarVertical.get()) {
         name =  "Overlay Scrollbar Vertical Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace WebCore