Invalidate LayoutView when the URL bar is hidden on short pages.

third_party/WebKit/Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 1540 matching lines @@
     m_viewportConstrainedObjects->remove(object);
 
     if (ScrollingCoordinator* scrollingCoordinator =
             this->scrollingCoordinator())
       scrollingCoordinator->frameViewFixedObjectsDidChange(this);
   }
 }
 
 void FrameView::viewportSizeChanged(bool widthChanged, bool heightChanged) {
   DCHECK(widthChanged || heightChanged);
+  DCHECK(m_frame->host());
 
   if (LayoutViewItem layoutView = this->layoutViewItem()) {
     if (layoutView.usesCompositing())
       layoutView.compositor()->frameViewDidChangeSize();
   }
 
   // Ensure the root scroller compositing layers update geometry in response to
   // the URL bar resizing.
-  if (m_frame->isMainFrame()) {
-    m_frame->document()
-        ->frameHost()
-        ->globalRootScrollerController()
-        .mainFrameViewResized();
-  }
+  if (m_frame->isMainFrame())
+    m_frame->host()->globalRootScrollerController().mainFrameViewResized();
 
   showOverlayScrollbars();
-  if (RuntimeEnabledFeatures::rootLayerScrollingEnabled()) {
+
+  bool rootLayerScrollingEnabled =
+      RuntimeEnabledFeatures::rootLayerScrollingEnabled();
+  if (rootLayerScrollingEnabled) {
     // The background must be repainted when the FrameView is resized, even if
     // the initial containing block does not change (so we can't rely on layout
     // to issue the invalidation).  This is because the background fills the
     // main GraphicsLayer, which takes the size of the layout viewport.
     // TODO(skobes): Paint non-fixed backgrounds into the scrolling contents
     // layer and avoid this invalidation (http://crbug.com/568847).
     LayoutViewItem lvi = layoutViewItem();
     if (!lvi.isNull())
       lvi.setShouldDoFullPaintInvalidation();
   }
 
   if (RuntimeEnabledFeatures::inertTopControlsEnabled() && layoutView() &&
-      layoutView()->style()->hasFixedBackgroundImage()) {
-    // In the case where we don't change layout size from top control resizes,
-    // we wont perform a layout. If we have a fixed background image however,
-    // the background layer needs to get resized so we should request a layout
-    // explicitly.
-    PaintLayer* layer = layoutView()->layer();
-    if (layoutView()->compositor()->needsFixedRootBackgroundLayer(layer)) {
-      setNeedsLayout();
-    } else if (!RuntimeEnabledFeatures::rootLayerScrollingEnabled()) {
-      // If root layer scrolls is on, we've already issued a full invalidation
+      m_frame->isMainFrame() && m_frame->host()->browserControls().height()) {

[bokan, 2016/12/22 00:45:49]

This doesn't really apply to non-main frames (yet, document.rootScroller will
likely change that) and even for main frames should only occur when we're using
a mobile URL bar. I've added these conditions to prevent over-invalidation since
without the URL bar we'll invalidate from layout. I don't think it's an issue
but this prevents having to rebase a bunch of layout tests that don't expect
multiple invalidations.

+    if (layoutView()->style()->hasFixedBackgroundImage()) {
+      // In the case where we don't change layout size from top control resizes,
+      // we wont perform a layout. If we have a fixed background image however,
+      // the background layer needs to get resized so we should request a layout
+      // explicitly.
+      PaintLayer* layer = layoutView()->layer();
+      if (layoutView()->compositor()->needsFixedRootBackgroundLayer(layer)) {
+        setNeedsLayout();
+      } else if (!rootLayerScrollingEnabled) {
+        // If root layer scrolls is on, we've already issued a full invalidation
+        // above.
+        layoutView()->setShouldDoFullPaintInvalidationOnResizeIfNeeded(
+            widthChanged, heightChanged);
+      }
+    } else if (heightChanged && !rootLayerScrollingEnabled) {
+      // If the document rect doesn't fill the full view height, hiding the
+      // URL bar will expose area outside the current LayoutView so we need to
+      // paint additional background. If RLS is on, we've already invalidated
       // above.
-      layoutView()->setShouldDoFullPaintInvalidationOnResizeIfNeeded(
-          widthChanged, heightChanged);
+      LayoutViewItem lvi = layoutViewItem();
+      DCHECK(!lvi.isNull());
+      if (lvi.documentRect().height() < lvi.viewRect().height())
+        lvi.setShouldDoFullPaintInvalidation();
     }
   }
 
   if (!hasViewportConstrainedObjects())
     return;
 
   for (const auto& viewportConstrainedObject : *m_viewportConstrainedObjects) {
     LayoutObject* layoutObject = viewportConstrainedObject;
     const ComputedStyle& style = layoutObject->styleRef();
     if (widthChanged) {
@@ skipping 3261 matching lines @@
        reason < MainThreadScrollingReason::kMainThreadScrollingReasonCount;
        ++reason) {
     if (m_mainThreadScrollingReasonsCounter[reason] > 0) {
       reasons |= 1 << (reason - 1);
     }
   }
   return reasons;
 }
 
 }  // namespace blink