Add a Physical Web omnibox autocomplete provider

components/omnibox/browser/physical_web_provider.h

+// 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.
+
+#ifndef COMPONENTS_OMNIBOX_BROWSER_PHYSICAL_WEB_PROVIDER_H_
+#define COMPONENTS_OMNIBOX_BROWSER_PHYSICAL_WEB_PROVIDER_H_
+
+#include "components/omnibox/browser/autocomplete_input.h"
+#include "components/omnibox/browser/autocomplete_provider.h"
+
+class AutocompleteProviderClient;
+
+namespace base {
+class ListValue;
+}
+
+class PhysicalWebProvider : public AutocompleteProvider {
+public:
+  static PhysicalWebProvider* Create(AutocompleteProviderClient* client);
+
+  // AutocompleteProvider:
+  void Start(const AutocompleteInput& input, bool minimal_changes) override;
+  void Stop(bool clear_cached_results, bool due_to_user_inactivity) override;
+
+private:
+  PhysicalWebProvider(AutocompleteProviderClient* client);
+  ~PhysicalWebProvider() override;
+
+  // Adds a separate match item for each nearby URL, up to the maximum number of
+  // matches allowed by this provider. If the total number of nearby URLs

[Mark P, 2016/08/10 23:33:21]

nit: omit "by this provider"; it doesn't add anything useful in this context.

[Mark P, 2016/08/10 23:33:21]

First sentence: this should mention where the matches are being added and where
the URLs come from.  Are matches being encoded and stored in |metadata_list|? 
Somewhere else?  And where is the info on what matches exist coming from? 
Something injected?  Something in |metadata_list|.

[mattreynolds, 2016/08/11 01:25:03]

Done.

+  // exceeds this limit, one match is reserved for an overflow item.

[Mark P, 2016/08/10 23:33:21]

nit: "one match" -> "one slot"
(I assume you don't fill in this extra slot with a match.)

[mattreynolds, 2016/08/11 01:25:03]

The terminology is confusing since technically they are all AutocompleteMatches,
but I agree "slot" is clearer here.

+  void ConstructMatches(base::ListValue* metadata_list);
+
+  // Adds an overflow match item when the number of nearby URLs exceeds the
+  // maximum number of matches allowed by this provider. Selecting the overflow

[Mark P, 2016/08/10 23:33:21]

ditto same concerns about unclear what variables are being changed.

Also, in general would it make sense--and make the code simpler--to make this
function unconditional (always add something) and simply be smart about when to
call it?

[mattreynolds, 2016/08/11 01:25:03]

Makes sense, renamed to AppendOverflowItem and moved the conditional logic into
ConstructMatches since it already needs to consider whether there should be an
overflow item.

+  // item navigates to the Physical Web WebUI, which displays the full list of
+  // nearby URLs.
+  void AppendOverflowItemIfNecessary(base::ListValue* metadata_list);
+
+  AutocompleteProviderClient* client_;
+};
+
+#endif  // COMPONENTS_OMNIBOX_BROWSER_PHYSICAL_WEB_PROVIDER_H_