[TooManyTabs] Add TabNavigationThrottle

content/browser/web_contents/web_contents_impl.cc

Index: content/browser/web_contents/web_contents_impl.cc
diff --git a/content/browser/web_contents/web_contents_impl.cc b/content/browser/web_contents/web_contents_impl.cc
index ffba46b099c9192c32330841cccdb96e87b58595..6aa993645392f613db8bb173a6debeb89d6401f6 100644
--- a/content/browser/web_contents/web_contents_impl.cc
+++ b/content/browser/web_contents/web_contents_impl.cc
@@ -1505,6 +1505,10 @@ void WebContentsImpl::WasHidden() {
   should_normally_be_visible_ = false;
 }
 
+bool WebContentsImpl::IsVisible() const {
+  return should_normally_be_visible_;
+}
+
 void WebContentsImpl::WasOccluded() {
   if (capturer_count_ > 0)
     return;