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 5046d23ada20bf468f9793fed69245effa399244..c89ad2829138e6d6125766df5c79a06362ad8341 100644
--- a/Source/core/loader/FrameLoader.cpp
+++ b/Source/core/loader/FrameLoader.cpp
@@ -49,8 +49,10 @@
 #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"
@@ -183,6 +185,12 @@ void FrameLoader::saveScrollState()
         return;
 
     m_currentItem->setScrollPoint(m_frame->view()->scrollPosition());
+
+    if (m_frame->document()->settings()->pinchVirtualViewportEnabled())
+        m_currentItem->setPinchViewportScrollPoint(m_frame->host()->pinchViewport().visibleRect().location());
+    else
+        m_currentItem->setPinchViewportScrollPoint(FloatPoint(-1, -1));
+
     if (m_frame->isMainFrame() && !m_frame->page()->inspectorController().deviceEmulationEnabled())
         m_currentItem->setPageScaleFactor(m_frame->page()->pageScaleFactor());
 
@@ -986,15 +994,30 @@ 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();
+    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);

[aelias_OOO_until_Jul13, 2014/05/07 08:06:03]

In the legacy historyitem case, I think you also need to subtract the computed
pinchViewportOffset from the scrollPoint.  Your unit test fails to catch this
bug because the outer viewport is at the bottom right of the document in that
test case.

[aelias_OOO_until_Jul13, 2014/05/07 08:41:35]

Ignore that comment, since I realized it has to always be zero in the
non-bottom-right case anyway.  lgtm as is.

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