JavaScript dialogs cause a page to lose fullscreen.

content/browser/web_contents/web_contents_impl.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/web_contents/web_contents_impl.h"
 
 #include <stddef.h>
 
 #include <cmath>
 #include <utility>
@@ skipping 4407 matching lines @@
   render_view_host_delegate_view_->ShowContextMenu(render_frame_host,
                                                    context_menu_params);
 }
 
 void WebContentsImpl::RunJavaScriptDialog(RenderFrameHost* render_frame_host,
                                           const base::string16& message,
                                           const base::string16& default_prompt,
                                           const GURL& frame_url,
                                           JavaScriptDialogType dialog_type,
                                           IPC::Message* reply_msg) {
+  // Running a dialog causes an exit to webpage-initiated fullscreen.
+  // http://crbug.com/728276
+  if (IsFullscreenForCurrentTab())
+    ExitFullscreen(false);

[Matt Giuca, 2017/06/09 06:16:37]

I think this should be true... documentation says "|will_cause_resize| indicates
whether the fullscreen change causes a view resize. e.g. This will be false when
going from tab fullscreen to browser fullscreen."

Seems like it should be true in this case.

[Avi (use Gerrit), 2017/06/09 14:36:23]

Done.

+
   // Suppress JavaScript dialogs when requested. Also suppress messages when
   // showing an interstitial as it's shown over the previous page and we don't
   // want the hidden page's dialogs to interfere with the interstitial.
   bool suppress_this_message =
       ShowingInterstitialPage() || !delegate_ ||
       delegate_->ShouldSuppressDialogs(this) ||
       !delegate_->GetJavaScriptDialogManager(this);
 
   if (!suppress_this_message) {
     is_showing_javascript_dialog_ = true;
@@ skipping 12 matching lines @@
     OnDialogClosed(render_frame_host->GetProcess()->GetID(),
                    render_frame_host->GetRoutingID(), reply_msg,
                    true, false, base::string16());
   }
 }
 
 void WebContentsImpl::RunBeforeUnloadConfirm(
     RenderFrameHost* render_frame_host,
     bool is_reload,
     IPC::Message* reply_msg) {
+  // Running a dialog causes an exit to webpage-initiated fullscreen.
+  // http://crbug.com/728276
+  if (IsFullscreenForCurrentTab())
+    ExitFullscreen(false);

[Matt Giuca, 2017/06/09 06:16:37]

Same as above.

[Avi (use Gerrit), 2017/06/09 14:36:23]

Done.

+
   RenderFrameHostImpl* rfhi =
       static_cast<RenderFrameHostImpl*>(render_frame_host);
   if (delegate_)
     delegate_->WillRunBeforeUnloadConfirm();
 
   bool suppress_this_message =
       !rfhi->is_active() ||
       ShowingInterstitialPage() || !delegate_ ||
       delegate_->ShouldSuppressDialogs(this) ||
       !delegate_->GetJavaScriptDialogManager(this);
@@ skipping 1250 matching lines @@
     new_root->SetOriginalOpener(opener->frame_tree()->root());
 
     if (!opener_suppressed) {
       new_root->SetOpener(opener);
       created_with_opener_ = true;
     }
   }
 }
 
 }  // namespace content