Remove about:srcdoc url conversion.

content/browser/site_instance_impl.cc

Index: content/browser/site_instance_impl.cc
diff --git a/content/browser/site_instance_impl.cc b/content/browser/site_instance_impl.cc
index 7980783a7d3ed0acfe3da00d14a192471abd8e75..83547cd7748094d1388fab96fb516e939d2d8da1 100644
--- a/content/browser/site_instance_impl.cc
+++ b/content/browser/site_instance_impl.cc
@@ -316,10 +316,9 @@ bool SiteInstance::IsSameWebSite(BrowserContext* browser_context,
   if (!src_url.is_valid() || !dest_url.is_valid())
     return false;
 
-  // If the destination url is just a blank page, we treat them as part of the
-  // same site.
-  GURL blank_page(url::kAboutBlankURL);
-  if (dest_url == blank_page)
+  // If the destination url is just about:blank or about:srcdoc, we treat them
+  // as part of the same site.
+  if (dest_url == url::kAboutBlankURL || dest_url == content::kAboutSrcDocURL)
     return true;
 
   // If the schemes differ, they aren't part of the same site.