Fix main thread top controls scrolling to mirror CC.

third_party/WebKit/Source/web/WebViewImpl.cpp

 /*
  * Copyright (C) 2011, 2012 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 1809 matching lines @@
 
     WebLocalFrameImpl* mainFrame = mainFrameImpl();
     if (!mainFrame)
         return;
 
     FrameView* view = mainFrame->frameView();
     if (!view)
         return;
 
     VisualViewport& visualViewport = page()->frameHost().visualViewport();
-    float topControlsViewportAdjustment = topControls().layoutHeight() - topControls().contentOffset();
-    visualViewport.setTopControlsAdjustment(topControlsViewportAdjustment);
 
-    // Shrink the FrameView by the amount that will maintain the aspect-ratio with the VisualViewport.
-    view->setTopControlsViewportAdjustment(topControlsViewportAdjustment / minimumPageScaleFactor());
+    {
+        // This object will save the current visual viewport offset w.r.t. the
+        // document and restore it when the object goes out of scope. It's
+        // needed since the top controls adjustment will change the maximum
+        // scroll offset and we may need to reposition them to keep the user's
+        // apparent position unchanged.
+        ResizeViewportAnchor anchor(*view, visualViewport);
+
+        float topControlsViewportAdjustment =
+            topControls().layoutHeight() - topControls().contentOffset();
+        visualViewport.setTopControlsAdjustment(topControlsViewportAdjustment);
+
+        // Since the FrameView is sized to be the visual viewport at minimum
+        // scale, its adjustment must also be scaled by the minimum scale.
+        view->setTopControlsViewportAdjustment(
+            topControlsViewportAdjustment / minimumPageScaleFactor());
+
+        // Clamp the scroll offset of each viewport now that their bounds have
+        // changed. We'll try to restore hte saved scroll offset when anchor

[majidvp, 2016/04/01 17:09:36]

s/hte/the/

[bokan, 2016/04/05 17:11:40]

Done.

+        // goes out of scope.
+        visualViewport.clampToBoundaries();
+        view->setScrollPosition(view->scrollPositionDouble(), ProgrammaticScroll);

[majidvp, 2016/04/01 17:09:36]

Shouldn't this be unnecessary? The anchor sets the scroll position which should
also
clamp if necessary.

[bokan, 2016/04/05 17:11:40]

But the anchor needs the viewports to be at their clamped locations in order to
calculate where to restore them to (it works based on deltas in order to prevent
scrolling the layout viewport if it's unneeded). Admittedly this is more
appropriate in the anchoring code so I moved it there.

+    }
 }
 
 TopControls& WebViewImpl::topControls()
 {
     return page()->frameHost().topControls();
 }
 
 void WebViewImpl::resizeViewWhileAnchored(FrameView* view)
 {
     ASSERT(mainFrameImpl() && mainFrameImpl()->frame()->isLocalFrame());
@@ skipping 2478 matching lines @@
     const WebFloatSize& elasticOverscrollDelta,
     float pageScaleDelta,
     float topControlsShownRatioDelta)
 {
     if (!mainFrameImpl())
         return;
     FrameView* frameView = mainFrameImpl()->frameView();
     if (!frameView)
         return;
 
+    ScrollableArea* layoutViewport = frameView->layoutViewportScrollableArea();
+    VisualViewport& visualViewport = page()->frameHost().visualViewport();
+
+    // Store the desired offsets for visual and layout viewports before setting
+    // the top controls ratio since doing so will change the bounds and move the
+    // viewports to keep the offsets valid. The compositor may have already done
+    // that so we don't want to double apply the deltas here.
+    FloatPoint visualViewportOffset = visualViewport.visibleRect().location();
+    visualViewportOffset.move(
+        visualViewportDelta.width,
+        visualViewportDelta.height);
+    DoublePoint layoutViewportPosition = layoutViewport->scrollPositionDouble()
+        + DoubleSize(layoutViewportDelta.width, layoutViewportDelta.height);
+
     topControls().setShownRatio(topControls().shownRatio() + topControlsShownRatioDelta);
 
-    FloatPoint visualViewportOffset = page()->frameHost().visualViewport().visibleRect().location();
-    visualViewportOffset.move(visualViewportDelta.width, visualViewportDelta.height);
     setPageScaleFactorAndLocation(pageScaleFactor() * pageScaleDelta, visualViewportOffset);
 
     if (pageScaleDelta != 1) {
         m_doubleTapZoomPending = false;
-        page()->frameHost().visualViewport().userDidChangeScale();
+        visualViewport.userDidChangeScale();
     }
 
     m_elasticOverscroll += elasticOverscrollDelta;
     frameView->didUpdateElasticOverscroll();
 
-    ScrollableArea* layoutViewport = frameView->layoutViewportScrollableArea();
-
-    DoublePoint layoutViewportPosition = layoutViewport->scrollPositionDouble()
-        + DoubleSize(layoutViewportDelta.width, layoutViewportDelta.height);
-
     if (layoutViewport->scrollPositionDouble() != layoutViewportPosition) {
         layoutViewport->setScrollPosition(layoutViewportPosition, CompositorScroll);
         if (DocumentLoader* documentLoader = mainFrameImpl()->frame()->loader().documentLoader())
             documentLoader->initialScrollState().wasScrolledByUser = true;
     }
 }
 
 void WebViewImpl::recordFrameTimingEvent(FrameTimingEventType eventType, int64_t FrameId, const WebVector<WebFrameTimingEvent>& events)
 {
     Frame* frame = m_page ? m_page->mainFrame() : 0;
@@ skipping 202 matching lines @@
 {
     // TODO(oshima): Investigate if this should return the ScreenInfo's scale factor rather than
     // page's scale factor, which can be 1 in use-zoom-for-dsf mode.
     if (!page())
         return 1;
 
     return page()->deviceScaleFactor();
 }
 
 } // namespace blink