Fix scroll restoration when exiting fullscreen mode.

third_party/WebKit/Source/web/FullscreenController.cpp

Index: third_party/WebKit/Source/web/FullscreenController.cpp
diff --git a/third_party/WebKit/Source/web/FullscreenController.cpp b/third_party/WebKit/Source/web/FullscreenController.cpp
index 1efda9e2b976de93c0f7c4bc4f1ae178c8d5e812..da1e25274920e5162db0ffb354eee3ddd9c864a4 100644
--- a/third_party/WebKit/Source/web/FullscreenController.cpp
+++ b/third_party/WebKit/Source/web/FullscreenController.cpp
@@ -54,6 +54,7 @@ PassOwnPtrWillBeRawPtr<FullscreenController> FullscreenController::create(WebVie
 
 FullscreenController::FullscreenController(WebViewImpl* webViewImpl)
     : m_webViewImpl(webViewImpl)
+    , m_haveEnteredFullscreen(false)
     , m_exitFullscreenPageScaleFactor(0)
     , m_isCancelingFullScreen(false)
 {
@@ -71,15 +72,12 @@ void FullscreenController::didEnterFullScreen()
     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());
@@ -118,13 +116,12 @@ void FullscreenController::didExitFullScreen()
                 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);
@@ -150,6 +147,14 @@ void FullscreenController::enterFullScreenForElement(Element* element)
         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()) {