Show Physical Web zero-suggest omnibox suggestions after query is deleted

components/omnibox/browser/physical_web_provider.cc

 // Copyright (c) 2016 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/physical_web_provider.h"
 
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 57 matching lines @@
   }
 
   physical_web::PhysicalWebDataSource* data_source =
       client_->GetPhysicalWebDataSource();
   if (!data_source) {
     done_ = true;
     nearby_url_count_ = 0;
     return;
   }
 
-  if (input.from_omnibox_focus()) {
+  if (input.from_omnibox_focus() || input.text().empty()) {
     ConstructZeroSuggestMatches(data_source->GetMetadataList());
 
     if (!matches_.empty()) {
       had_physical_web_suggestions_ = true;
       had_physical_web_suggestions_at_focus_or_later_ = true;
     }
 
     if (!zero_suggest_enabled_) {
       matches_.clear();
     }
 
     // In zero-suggest, Physical Web matches should never be default. If the
     // omnibox input is non-empty and we have at least one Physical Web match,
     // add the current URL as the default so that hitting enter after focusing
     // the omnibox causes the current page to reload. If the input field is
     // empty, no default match is required.
     if (!matches_.empty() && !input.text().empty()) {

[Mark P, 2017/01/24 19:06:12]

I don't think this test is exactly right anymore.
On a non-NTP, if I delete all the input text, I still see the current page as
the top suggestion.
I guess some other provider is adding the current page URL as a suggestion, so
in some sense the fact that we don't isn't an issue.  Yet, if we're relying on
some other provider to add it in this case (user modified a non-NTP URL to an
empty string), we should at least comment on this reliance here.  Or revise the
code so we don't rely on it. :-)

[mattreynolds, 2017/01/24 22:41:54]

I think that's an Android bug, we should never display only the verbatim match.
On iOS, no suggestions are shown when you clear the input, and if I try to call
VerbatimMatchForURL with an empty input I hit a DCHECK.

Is a default match actually required in this case? IIUC, a default is added to
support focus->enter for reloading the page. If the user has already modified
the input, do we care about adding the verbatim match?

[Mark P, 2017/01/25 20:19:47]

Filed crbug.com/685332.  It seems straightforward to fix.  Can I assign it to
you, as this is the area you're working in right now.
Good point.

[mattreynolds, 2017/01/25 22:01:52]

Thanks, I'll look into it.

       matches_.push_back(VerbatimMatchForURL(
           client_, input, input.current_url(), history_url_provider_, -1));
     }
   } else {
     ConstructQuerySuggestMatches(data_source->GetMetadataList(), input);
 
     if (!matches_.empty()) {
       had_physical_web_suggestions_ = true;
       had_physical_web_suggestions_at_focus_or_later_ = true;
     }
@@ skipping 167 matching lines @@
       AutocompleteInput::FormattedStringWithEquivalentMeaning(
           url, match.contents, client_->GetSchemeClassifier());
 
   match.description =
       l10n_util::GetStringUTF16(IDS_PHYSICAL_WEB_OVERFLOW_DESCRIPTION);
   match.description_class.push_back(
       ACMatchClassification(0, ACMatchClassification::NONE));
 
   matches_.push_back(match);
 }