Mark URLs with empty schemes as invalid.

components/url_formatter/url_fixer.cc

Index: components/url_formatter/url_fixer.cc
diff --git a/components/url_formatter/url_fixer.cc b/components/url_formatter/url_fixer.cc
index 53abe4e0c4a910aa2a065160af3f35c0533352be..cf60f43d3b57874a0ebe1c5ccda1e2817ea3e961 100644
--- a/components/url_formatter/url_fixer.cc
+++ b/components/url_formatter/url_fixer.cc
@@ -480,7 +480,8 @@ std::string SegmentURLInternal(std::string* text, url::Parsed* parts) {
 
   // Construct the text to parse by inserting the scheme.
   std::string inserted_text(scheme);
-  inserted_text.append(url::kStandardSchemeSeparator);
+  if (first_nonwhite == text->end() || *first_nonwhite != ':')

[Peter Kasting, 2016/09/29 04:54:12]

Not sure I really understand this change.  Why convert ":foo" to "http:foo" and
not "http://foo" or "http://:foo"?  Seems like "http://foo" is better if we're
trying to make something invalid become valid, and "http://:foo" is better if
we're intentionally trying to not care about this case and let it fail.

+    inserted_text.append(url::kStandardSchemeSeparator);  // Add "://".
   std::string text_to_parse(text->begin(), first_nonwhite);
   text_to_parse.append(inserted_text);
   text_to_parse.append(first_nonwhite, text->end());