Hide fullscreen rotation jank

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 60 matching lines @@
   if (state_ != State::kEnteringFullscreen)
     return;
 
   UpdatePageScaleConstraints(false);
   web_view_base_->SetPageScaleFactor(1.0f);
   if (web_view_base_->MainFrame()->IsWebLocalFrame())
     web_view_base_->MainFrame()->SetScrollOffset(WebSize());
   web_view_base_->SetVisualViewportOffset(FloatPoint());
 
   state_ = State::kFullscreen;
+  web_view_base_->LayerTreeView()->SetIsFullscreen(true);
 
   // Notify all local frames that we have entered fullscreen.
   for (Frame* frame = web_view_base_->GetPage()->MainFrame(); frame;
        frame = frame->Tree().TraverseNext()) {
     if (!frame->IsLocalFrame())
       continue;
     if (Document* document = ToLocalFrame(frame)->GetDocument()) {
       if (Fullscreen* fullscreen = Fullscreen::FromIfExists(*document))
         fullscreen->DidEnterFullscreen();
     }
@@ skipping 168 matching lines @@
 
   web_view_base_->SetPageScaleFactor(initial_page_scale_factor_);
   if (web_view_base_->MainFrame()->IsWebLocalFrame())
     web_view_base_->MainFrame()->SetScrollOffset(
         WebSize(initial_scroll_offset_));
   web_view_base_->SetVisualViewportOffset(initial_visual_viewport_offset_);
   // Background color override was already restored when
   // fullscreenElementChanged([..], nullptr) was called while exiting.
 
   state_ = State::kInitial;
+  web_view_base_->LayerTreeView()->SetIsFullscreen(false);

[Khushal, 2017/05/24 02:12:24]

Why not do this in DidExitFullScreen?

[steimel, 2017/05/24 19:32:58]

To me it seemed to make more sense that is_fullscreen becomes false when state_
becomes kInitial as opposed to kNeedsScrollAndStateRestore. WDYT?

[Khushal, 2017/05/25 03:33:40]

The kNeedsScrollAndStateRestore is needed for changes that can happen only after
layout. Just setting the fullscreen state on the LayerTreeHost doesn't need to
wait for that.

[steimel, 2017/06/06 03:07:53]

Done.

 }
 
 void FullscreenController::UpdatePageScaleConstraints(bool remove_constraints) {
   PageScaleConstraints fullscreen_constraints;
   if (!remove_constraints) {
     fullscreen_constraints = PageScaleConstraints(1.0, 1.0, 1.0);
     fullscreen_constraints.layout_size = FloatSize(web_view_base_->Size());
   }
   web_view_base_->GetPageScaleConstraintsSet().SetFullscreenConstraints(
       fullscreen_constraints);
   web_view_base_->GetPageScaleConstraintsSet().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.
   web_view_base_->DidChangeContentsSize();
   if (web_view_base_->MainFrameImpl() &&
       web_view_base_->MainFrameImpl()->GetFrameView())
     web_view_base_->MainFrameImpl()->GetFrameView()->SetNeedsLayout();
 
   web_view_base_->UpdateMainFrameLayoutSize();
 }
 
 }  // namespace blink