Fix scroll restoration when exiting fullscreen mode.

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 36 matching lines @@
 
 namespace blink {
 
 PassOwnPtrWillBeRawPtr<FullscreenController> FullscreenController::create(WebViewImpl* webViewImpl)
 {
     return adoptPtrWillBeNoop(new FullscreenController(webViewImpl));
 }
 
 FullscreenController::FullscreenController(WebViewImpl* webViewImpl)
     : m_webViewImpl(webViewImpl)
+    , m_haveEnteredFullscreen(false)
     , m_exitFullscreenPageScaleFactor(0)
     , m_isCancelingFullScreen(false)
 {
 }
 
 void FullscreenController::didEnterFullScreen()
 {
     if (!m_provisionalFullScreenElement)
         return;
 
     RefPtrWillBeRawPtr<Element> element = m_provisionalFullScreenElement.release();
     Document& document = element->document();
     m_fullScreenFrame = document.frame();
 
     if (!m_fullScreenFrame)
         return;
 
-    if (!m_exitFullscreenPageScaleFactor) {
-        m_exitFullscreenPageScaleFactor = m_webViewImpl->pageScaleFactor();
-        m_exitFullscreenScrollOffset = m_webViewImpl->mainFrame()->scrollOffset();
-        m_exitFullscreenVisualViewportOffset = m_webViewImpl->visualViewportOffset();
-
+    if (!m_haveEnteredFullscreen) {
         updatePageScaleConstraints(false);
         m_webViewImpl->setPageScaleFactor(1.0f);
         m_webViewImpl->mainFrame()->setScrollOffset(WebSize());
         m_webViewImpl->setVisualViewportOffset(FloatPoint());
+        m_haveEnteredFullscreen = true;
     }
 
     Fullscreen::from(document).didEnterFullScreenForElement(element.get());
     ASSERT(Fullscreen::currentFullScreenElementFrom(document) == element);
 
     if (isHTMLVideoElement(element)) {
         HTMLVideoElement* videoElement = toHTMLVideoElement(element);
         if (videoElement->usesOverlayFullscreenVideo()) {
             if (videoElement->webMediaPlayer()
                 // FIXME: There is no embedder-side handling in layout test mode.
@@ skipping 18 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_exitFullscreenPageScaleFactor) {
+                if (m_haveEnteredFullscreen) {
                     updatePageScaleConstraints(true);
                     m_webViewImpl->setPageScaleFactor(m_exitFullscreenPageScaleFactor);
                     m_webViewImpl->mainFrame()->setScrollOffset(WebSize(m_exitFullscreenScrollOffset));
                     m_webViewImpl->setVisualViewportOffset(m_exitFullscreenVisualViewportOffset);
-                    m_exitFullscreenPageScaleFactor = 0;
-                    m_exitFullscreenScrollOffset = IntSize();
+                    m_haveEnteredFullscreen = false;
                 }
 
                 fullscreen->didExitFullScreenForElement(0);
             }
         }
     }
 
     m_fullScreenFrame.clear();
 }
 
 void FullscreenController::enterFullScreenForElement(Element* element)
 {
     // We are already transitioning to fullscreen for a different element.
     if (m_provisionalFullScreenElement) {
         m_provisionalFullScreenElement = element;
         return;
     }
 
     // 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

[scheib, 2015/12/01 00:30:18]

Comments might as well wrap to 80 chars. (optional)

[bokan, 2015/12/01 20:46:10]

Done.

+    // is called, a Resize has already occured, clamping the scroll offset.
+    if (!m_haveEnteredFullscreen) {
+        m_exitFullscreenPageScaleFactor = m_webViewImpl->pageScaleFactor();
+        m_exitFullscreenScrollOffset = m_webViewImpl->mainFrame()->scrollOffset();
+        m_exitFullscreenVisualViewportOffset = m_webViewImpl->visualViewportOffset();
+    }
+
     // We need to transition to fullscreen mode.
     WebLocalFrameImpl* frame = WebLocalFrameImpl::fromFrame(element->document().frame());
     if (frame && frame->client()) {
         frame->client()->enterFullscreen();
         m_provisionalFullScreenElement = element;
     }
 }
 
 void FullscreenController::exitFullScreenForElement(Element* element)
 {
@@ skipping 33 matching lines @@
 }
 
 DEFINE_TRACE(FullscreenController)
 {
     visitor->trace(m_provisionalFullScreenElement);
     visitor->trace(m_fullScreenFrame);
 }
 
 } // namespace blink