Expose RenderFrameHost::GetLastCommittedOrigin().

It is an error to call this unless the RFH is current -- similar to
GetLastCommittedURL, but we actually enforce it.

There are two pending CLs that will want to use this: 1413853005 and 1465533008.

BUG=498580
[email protected]

Review URL: https://codereview.chromium.org/1475433002

Cr-Commit-Position: refs/heads/master@{#361722}
diff --git a/url/scheme_host_port.h b/url/scheme_host_port.h
index 6e35a25..3aca558 100644
--- a/url/scheme_host_port.h
+++ b/url/scheme_host_port.h
@@ -116,8 +116,8 @@
   // themselves). Unique origins, on the other hand, would not.
   bool Equals(const SchemeHostPort& other) const;
 
-  // Allows SchemeHostPort to used as a key in STL (for example, a std::set or
-  // std::map).
+  // Allows SchemeHostPort to be used as a key in STL (for example, a std::set
+  // or std::map).
   bool operator<(const SchemeHostPort& other) const;
 
  private: