Added pinch viewport offset to history item.

Source/core/loader/FrameLoader.cpp

Index: Source/core/loader/FrameLoader.cpp
diff --git a/Source/core/loader/FrameLoader.cpp b/Source/core/loader/FrameLoader.cpp
index 0b14245bc83460dec7287c89fb7b53ddc7fb2ccb..3afac9bdfc29916a35943abf1c2c866445f93c9c 100644
--- a/Source/core/loader/FrameLoader.cpp
+++ b/Source/core/loader/FrameLoader.cpp
@@ -50,8 +50,10 @@
 #include "core/fetch/ResourceFetcher.h"
 #include "core/fetch/ResourceLoader.h"
 #include "core/frame/DOMWindow.h"
+#include "core/frame/FrameHost.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
+#include "core/frame/PinchViewport.h"
 #include "core/frame/csp/ContentSecurityPolicy.h"
 #include "core/html/HTMLFormElement.h"
 #include "core/html/HTMLFrameOwnerElement.h"
@@ -184,6 +186,12 @@ void FrameLoader::saveScrollState()
         return;
 
     m_currentItem->setScrollPoint(m_frame->view()->scrollPosition());
+
+    if (m_frame->document()->settings()->pinchVirtualViewportEnabled())

[abarth-chromium, 2014/05/09 14:11:23]

m_frame->settings()

[bokan, 2014/05/09 14:32:57]

Done.

+        m_currentItem->setPinchViewportScrollPoint(m_frame->host()->pinchViewport().visibleRect().location());
+    else
+        m_currentItem->setPinchViewportScrollPoint(FloatPoint(-1, -1));

[abarth-chromium, 2014/05/09 14:11:23]

Can we use something other than (-1, -1) here?  That could be a valid value for
the scroll point.  If the value isn't relevant, please use FloatPoint().  If you
need to signal "no value", please do that explicitly instead of using in-band
signaling.

[bokan, 2014/05/09 14:32:57]

It's not a valid value for the pinch viewport's scroll. It's strictly contained
within the main frame. Also, this should also go away after a few releases, it's
just so HistoryItems with scroll offsets from the old pinch path can still be
restored reasonably.

+
     if (m_frame->isMainFrame() && !m_frame->page()->inspectorController().deviceEmulationEnabled())
         m_currentItem->setPageScaleFactor(m_frame->page()->pageScaleFactor());
 
@@ -992,15 +1000,30 @@ void FrameLoader::restoreScrollPositionAndViewState()
     // page height increases, 3. ignore clamp detection after load completes
     // because that may be because the page will never reach its previous
     // height.
-    bool canRestoreWithoutClamping = view->clampOffsetAtScale(m_currentItem->scrollPoint(), m_currentItem->pageScaleFactor()) == m_currentItem->scrollPoint();
+    float mainFrameScale = m_frame->document()->settings()->pinchVirtualViewportEnabled() ? 1 : m_currentItem->pageScaleFactor();

[abarth-chromium, 2014/05/09 14:11:23]

m_frame->settings()

[bokan, 2014/05/09 14:32:57]

Done.

+    bool canRestoreWithoutClamping = view->clampOffsetAtScale(m_currentItem->scrollPoint(), mainFrameScale) == m_currentItem->scrollPoint();
     bool canRestoreWithoutAnnoyingUser = !view->wasScrolledByUser() && (canRestoreWithoutClamping || m_state == FrameStateComplete);
     if (!canRestoreWithoutAnnoyingUser)
         return;
 
-    if (m_frame->isMainFrame() && m_currentItem->pageScaleFactor())
-        m_frame->page()->setPageScaleFactor(m_currentItem->pageScaleFactor(), m_currentItem->scrollPoint());
-    else
+    if (m_frame->isMainFrame() && m_currentItem->pageScaleFactor()) {
+        FloatPoint pinchViewportOffset(m_currentItem->pinchViewportScrollPoint());
+        IntPoint frameScrollOffset(m_currentItem->scrollPoint());
+
+        m_frame->page()->setPageScaleFactor(m_currentItem->pageScaleFactor(), frameScrollOffset);
+
+        if (m_frame->document()->settings()->pinchVirtualViewportEnabled()) {
+            // If the pinch viewport's offset is (-1, -1) it means the history item
+            // is an old version of HistoryItem so distribute the scroll between
+            // the main frame and the pinch viewport as best as we can.
+            if (pinchViewportOffset.x() == -1 && pinchViewportOffset.y() == -1)

[abarth-chromium, 2014/05/09 14:11:23]

Again, please don't use in-band signaling.

+                pinchViewportOffset = IntPoint(frameScrollOffset - view->scrollPosition());

[abarth-chromium, 2014/05/09 14:11:23]

Why an IntPoint?

[bokan, 2014/05/09 14:32:57]

Done. Changed to FloatPoint.

+
+            m_frame->host()->pinchViewport().setLocation(pinchViewportOffset);
+        }
+    } else {
         view->setScrollPositionNonProgrammatically(m_currentItem->scrollPoint());
+    }
 
     if (m_frame->isMainFrame()) {
         if (ScrollingCoordinator* scrollingCoordinator = m_frame->page()->scrollingCoordinator())