Ensure nearby URL count metric is properly initialized

components/omnibox/browser/physical_web_provider.h

Index: components/omnibox/browser/physical_web_provider.h
diff --git a/components/omnibox/browser/physical_web_provider.h b/components/omnibox/browser/physical_web_provider.h
index cab09c5c98296ab58b1616f2d42abdacdf80101c..3085d46d8bf50d29fc95f4074ee38c9931d4fbf6 100644
--- a/components/omnibox/browser/physical_web_provider.h
+++ b/components/omnibox/browser/physical_web_provider.h
@@ -47,6 +47,10 @@ class PhysicalWebProvider : public AutocompleteProvider {
                       HistoryURLProvider* history_url_provider);
   ~PhysicalWebProvider() override;
 
+  // Called when a new omnibox session is started. For the purposes of this
+  // provider, a session begins when the omnibox is initially focused.
+  void BeginOmniboxSession();
+
   // When the user has focused the omnibox but not yet entered any text (i.e.,
   // the Zero Suggest case), calling this method adds a separate match item to
   // |matches_| for each nearby URL in |metadata_list|, up to the maximum number
@@ -79,9 +83,16 @@ class PhysicalWebProvider : public AutocompleteProvider {
   HistoryURLProvider* history_url_provider_;
 
   // The number of nearby Physical Web URLs when the provider last constructed
-  // matches.
+  // matches. Initialized to string::npos.
   size_t nearby_url_count_;
 
+  // The number of nearby Physical Web URLs when the omnibox input was last
+  // focused. Initialized to string::npos.
+  // This value is set when the omnibox is focused and recorded when the user
+  // selects an omnibox suggestion. If the value is still string::npos when the
+  // user makes a selection, it indicates the omnibox was never focused.
+  size_t nearby_url_count_at_focus_;
+
   // If true, provide suggestions when the user has focused the omnibox but has
   // not typed anything.
   bool zero_suggest_enabled_;