Add url::Origin::GetURL() to convert Origins to URLs without reparsing

url/origin.cc

Index: url/origin.cc
diff --git a/url/origin.cc b/url/origin.cc
index a14c8918d35bfbf4430d0d5c5d7ebee577639f95..97afd2a06dc05dbfc4c2505f7b22ca5993501e9b 100644
--- a/url/origin.cc
+++ b/url/origin.cc
@@ -65,6 +65,16 @@ std::string Origin::Serialize() const {
   return tuple_.Serialize();
 }
 
+GURL Origin::GetURL() const {
+  if (unique())
+    return GURL("null");

[Mike West, 2016/09/30 12:37:40]

Hrm. I think `GURL::GetOrigin()` returns an empty GURL for an invalid URL.
Perhaps it makes sense to return `GURL()` instead?

[Charlie Harrison, 2016/09/30 14:29:58]

GURL("null") == GURL() so that's fine.

I would like to maintain that GURL(origin.Serialize()) == origin.GetURL().

Done.

+
+  if (scheme() == kFileScheme)
+    return GURL("file://");
+
+  return tuple_.GetURL();
+}
+
 bool Origin::IsSameOriginWith(const Origin& other) const {
   if (unique_ || other.unique_)
     return false;