Add a feature for allowing popups during page unload.

BUG=1009032, 937569

Change-Id: I6bcf68a1b12c4bcc7acf1b3e6d7b966062137db4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1829484Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Avi Drissman <avi@chromium.org>
Auto-Submit: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#701097}

content/public/common/content_features.cc

@@ -23,6 +23,11 @@ const base::Feature kAllowContentInitiatedDataUrlNavigations{
     "AllowContentInitiatedDataUrlNavigations",
     base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Allows popups during page unloading.
+// TODO(https://crbug.com/937569): Remove this in Chrome 82.
+const base::Feature kAllowPopupsDuringPageUnload{
+    "AllowPopupsDuringPageUnload", base::FEATURE_DISABLED_BY_DEFAULT};
+
 // Accepts Origin-Signed HTTP Exchanges to be signed with certificates
 // that do not have CanSignHttpExchangesDraft extension.
 // TODO(https://crbug.com/862003): Remove when certificates with

content/public/common/content_features.h

@@ -19,6 +19,7 @@ namespace features {
 CONTENT_EXPORT extern const base::Feature kAllowActivationDelegationAttr;
 CONTENT_EXPORT extern const base::Feature
     kAllowContentInitiatedDataUrlNavigations;
+CONTENT_EXPORT extern const base::Feature kAllowPopupsDuringPageUnload;
 CONTENT_EXPORT extern const base::Feature
     kAllowSignedHTTPExchangeCertsWithoutExtension;
 CONTENT_EXPORT extern const base::Feature kAudioServiceAudioStreams;

content/renderer/render_view_impl.cc

@@ -1784,7 +1784,8 @@ bool RenderViewImpl::CanHandleGestureEvent() {
 bool RenderViewImpl::AllowPopupsDuringPageUnload() {
   const base::CommandLine& command_line =
       *base::CommandLine::ForCurrentProcess();
-  return command_line.HasSwitch(switches::kAllowPopupsDuringPageUnload);
+  return command_line.HasSwitch(switches::kAllowPopupsDuringPageUnload) ||
+         base::FeatureList::IsEnabled(features::kAllowPopupsDuringPageUnload);
 }
 
 bool RenderViewImpl::CanUpdateLayout() {