Wait until after layout when restoring scroll on exiting fullscreen.

third_party/WebKit/Source/web/FullscreenController.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 37 matching lines @@
 
 FullscreenController* FullscreenController::create(WebViewImpl* webViewImpl)
 {
     return new FullscreenController(webViewImpl);
 }
 
 FullscreenController::FullscreenController(WebViewImpl* webViewImpl)
     : m_webViewImpl(webViewImpl)
     , m_haveEnteredFullscreen(false)
     , m_exitFullscreenPageScaleFactor(0)
+    , m_needsScrollAndScaleRestore(false)
     , m_isCancelingFullScreen(false)
 {
 }
 
 void FullscreenController::didEnterFullscreen()
 {
     if (!m_provisionalFullScreenElement)
         return;
 
     Element* element = m_provisionalFullScreenElement.release();
@@ skipping 37 matching lines @@
                 // When the client exits from full screen we have to call fullyExitFullscreen to notify
                 // the document. While doing that, suppress notifications back to the client.
                 m_isCancelingFullScreen = true;
                 Fullscreen::fullyExitFullscreen(*document);
                 m_isCancelingFullScreen = false;
 
                 // If the video used overlay fullscreen mode, the background was made transparent. Restore the transparency.
                 if (isHTMLVideoElement(element) && m_webViewImpl->layerTreeView())
                     m_webViewImpl->layerTreeView()->setHasTransparentBackground(m_webViewImpl->isTransparent());
 
-                if (m_haveEnteredFullscreen) {
-                    m_webViewImpl->setPageScaleFactor(m_exitFullscreenPageScaleFactor);
-                    if (m_webViewImpl->mainFrame()->isWebLocalFrame())
-                        m_webViewImpl->mainFrame()->setScrollOffset(WebSize(m_exitFullscreenScrollOffset));
-                    m_webViewImpl->setVisualViewportOffset(m_exitFullscreenVisualViewportOffset);
-                }
+                // We need to wait until style and layout are updated in order
+                // to propertly restore scroll offsets since content may not be
+                // overflowing in the same way until they do.
+                if (m_haveEnteredFullscreen)
+                    m_needsScrollAndScaleRestore = true;
 
                 fullscreen->didExitFullscreen();
             }
         }
     }
 
     m_haveEnteredFullscreen = false;
     m_fullScreenFrame.clear();
 }
 
@@ skipping 14 matching lines @@
 
     // We are already in fullscreen mode.
     if (m_fullScreenFrame) {
         m_provisionalFullScreenElement = element;
         didEnterFullscreen();
         return;
     }
 
     // We need to store these values here rather than didEnterFullscreen since
     // by the time the latter is called, a Resize has already occured, clamping
-    // the scroll offset.
-    if (!m_haveEnteredFullscreen) {
+    // the scroll offset. Don't save values if we're still waiting to restore
+    // a previous set. This can happen if we exit and quickly reenter fullscreen
+    // without performing a layout.
+    if (!m_haveEnteredFullscreen && !m_needsScrollAndScaleRestore) {
         m_exitFullscreenPageScaleFactor = m_webViewImpl->pageScaleFactor();
         m_exitFullscreenScrollOffset = m_webViewImpl->mainFrame()->isWebLocalFrame() ? m_webViewImpl->mainFrame()->scrollOffset() : WebSize();
         m_exitFullscreenVisualViewportOffset = m_webViewImpl->visualViewportOffset();
     }
 
     // We need to transition to fullscreen mode.
     WebLocalFrameImpl* frame = WebLocalFrameImpl::fromFrame(element->document().frame());
     if (frame && frame->client()) {
         if (!Fullscreen::from(element->document()).forCrossProcessDescendant())
             frame->client()->enterFullscreen();
@@ skipping 26 matching lines @@
     if (!isFullscreen())
         return;
 
     updatePageScaleConstraints(false);
 
     Document* document = m_fullScreenFrame->document();
     if (Element* fullscreenElement = Fullscreen::currentFullScreenElementFrom(*document))
         Fullscreen::from(fullscreenElement->document()).didUpdateSize(*fullscreenElement);
 }
 
+void FullscreenController::didUpdateLayout()
+{
+    if (!m_needsScrollAndScaleRestore)
+        return;
+
+    // If we re-entered fullscreen before we could restore the scroll and scale
+    // don't try restoring them yet.
+    if (isFullscreen())
+        return;
+
+    m_webViewImpl->setPageScaleFactor(m_exitFullscreenPageScaleFactor);
+    if (m_webViewImpl->mainFrame()->isWebLocalFrame())
+        m_webViewImpl->mainFrame()->setScrollOffset(WebSize(m_exitFullscreenScrollOffset));
+    m_webViewImpl->setVisualViewportOffset(m_exitFullscreenVisualViewportOffset);
+    m_needsScrollAndScaleRestore = false;
+}
+
 void FullscreenController::updatePageScaleConstraints(bool removeConstraints)
 {
     PageScaleConstraints fullscreenConstraints;
     if (!removeConstraints) {
         fullscreenConstraints = PageScaleConstraints(1.0, 1.0, 1.0);
         fullscreenConstraints.layoutSize = FloatSize(m_webViewImpl->size());
     }
     m_webViewImpl->pageScaleConstraintsSet().setFullscreenConstraints(fullscreenConstraints);
     m_webViewImpl->pageScaleConstraintsSet().computeFinalConstraints();
 
     // Although we called computedFinalConstraints() above, the "final" constraints are not
     // actually final. They are still subject to scale factor clamping by contents size.
     // Normally they should be dirtied due to contents size mutation after layout, however the
     // contents size is not guaranteed to mutate, and the scale factor may remain unclamped.
     // Just fire the event again to ensure the final constraints pick up the latest contents size.
     m_webViewImpl->didChangeContentsSize();
     if (m_webViewImpl->mainFrameImpl() && m_webViewImpl->mainFrameImpl()->frameView())
         m_webViewImpl->mainFrameImpl()->frameView()->setNeedsLayout();
 
     m_webViewImpl->updateMainFrameLayoutSize();
 }
 
 DEFINE_TRACE(FullscreenController)
 {
     visitor->trace(m_provisionalFullScreenElement);
     visitor->trace(m_fullScreenFrame);
 }
 
 } // namespace blink