Don't try to create a verbatim match with an empty input.

components/omnibox/browser/clipboard_url_provider.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/omnibox/browser/clipboard_url_provider.h"
 
 #include "base/logging.h"
 #include "base/strings/utf_string_conversions.h"
 #include "components/omnibox/browser/autocomplete_input.h"
 #include "components/omnibox/browser/autocomplete_provider_client.h"
@@ skipping 12 matching lines @@
       clipboard_content_(clipboard_content),
       history_url_provider_(history_url_provider) {
   DCHECK(clipboard_content_);
 }
 
 ClipboardURLProvider::~ClipboardURLProvider() {}
 
 void ClipboardURLProvider::Start(const AutocompleteInput& input,
                                  bool minimal_changes) {
   matches_.clear();
+
+  // If the user started typing, do not offer clipboard based match.
   if (!input.from_omnibox_focus())
     return;
 
   GURL url;
+  // If the clipboard does not contain any URL, or the URL on the page is the
+  // same as the URL in the clipboard, early return.
   if (!clipboard_content_->GetRecentURLFromClipboard(&url) ||
       url == input.current_url())
     return;
 
   DCHECK(url.is_valid());
-  // Adds a default match. This match will be opened when the user presses "Go".
-  AutocompleteMatch verbatim_match = VerbatimMatchForURL(
-      client_, input, input.current_url(), history_url_provider_, -1);
-  if (verbatim_match.destination_url.is_valid())
-    matches_.push_back(verbatim_match);
+  // If the omnibox is not empty, adds a default match.

[sdefresne, 2016/07/05 10:08:56]

nit: I would use if (!input.text().empty())

[Mark P, 2016/07/06 18:56:47]

nit: adds -> add

[jif, 2016/07/11 15:09:36]

Done.

[jif, 2016/07/11 15:09:36]

Done.

+  // This match will be opened when the user presses "Enter".
+  if (input.text().length()) {
+    AutocompleteMatch verbatim_match = VerbatimMatchForURL(
+        client_, input, input.current_url(), history_url_provider_, -1);
+    if (verbatim_match.destination_url.is_valid())

[Mark P, 2016/07/06 18:56:47]

This if test shouldn't be necessary anymore.  (It should always be valid.)

[jif, 2016/07/11 15:09:36]

Good catch. Done.

+      matches_.push_back(verbatim_match);
+  }
 
-  // Add a clipboard match just below the verbatim match.
-  AutocompleteMatch match(this, verbatim_match.relevance - 1, false,
+  // Add the clipboard match. The relevance can be '1' because there can only be

[Mark P, 2016/07/06 18:56:47]

side comment: once iOS enables ZeroSuggest to most visited, a la Android, this
'1' will have to change.  You'll probably want a number more like 800 (so it
beats the default other zero suggest results).  You may want to change it now in
preparation.

[jif, 2016/07/11 15:09:36]

Done.

+  // 0 or 1 match before: more matches will appear once the user starts typing,
+  // but when the user starts typing the clipboard based match stops showing up.
+  AutocompleteMatch match(this, 1, false,
                           AutocompleteMatchType::CLIPBOARD);
   match.destination_url = url;
   match.contents.assign(url_formatter::FormatUrl(
       url, url_formatter::kFormatUrlOmitAll, net::UnescapeRule::SPACES,
       nullptr, nullptr, nullptr));
   AutocompleteMatch::ClassifyLocationInString(
       base::string16::npos, 0, match.contents.length(),
       ACMatchClassification::URL, &match.contents_class);
 
   match.description.assign(l10n_util::GetStringUTF16(IDS_LINK_FROM_CLIPBOARD));
   AutocompleteMatch::ClassifyLocationInString(
       base::string16::npos, 0, match.description.length(),
       ACMatchClassification::NONE, &match.description_class);
 
   // At least one match must be default, so if verbatim_match was invalid,
   // the clipboard match is allowed to be default.
   match.allowed_to_be_default_match = matches_.empty();
   matches_.push_back(match);
 }