Revert of Remove about:srcdoc url conversion.

chrome/browser/extensions/api/web_navigation/web_navigation_api_helpers.cc

Index: chrome/browser/extensions/api/web_navigation/web_navigation_api_helpers.cc
diff --git a/chrome/browser/extensions/api/web_navigation/web_navigation_api_helpers.cc b/chrome/browser/extensions/api/web_navigation/web_navigation_api_helpers.cc
index c3dd31c658f254dd7413f5d62b6de9a0d672edf4..3f1e5a4aa9900b1928d6fb2b720e1357d11962f7 100644
--- a/chrome/browser/extensions/api/web_navigation/web_navigation_api_helpers.cc
+++ b/chrome/browser/extensions/api/web_navigation/web_navigation_api_helpers.cc
@@ -64,6 +64,8 @@
 // Constructs and dispatches an onBeforeNavigate event.
 void DispatchOnBeforeNavigate(content::NavigationHandle* navigation_handle) {
   GURL url(navigation_handle->GetURL());
+  if (navigation_handle->IsSrcdoc())
+    url = GURL(content::kAboutSrcDocURL);
 
   web_navigation::OnBeforeNavigate::Details details;
   details.tab_id =
@@ -93,6 +95,9 @@
   content::RenderFrameHost* frame_host =
       navigation_handle->GetRenderFrameHost();
   ui::PageTransition transition_type = navigation_handle->GetPageTransition();
+
+  if (navigation_handle->IsSrcdoc())
+    url = GURL(content::kAboutSrcDocURL);
 
   std::unique_ptr<base::ListValue> args(new base::ListValue());
   std::unique_ptr<base::DictionaryValue> dict(new base::DictionaryValue());