[omnibox] Return documents after provider_max_matches_ with score 0.

Currently, the doc provider returns at most provider_max_matches_ docs, dropping
any additional docs returned from the server. With this CL, the provider returns
the remaining docs with a score of 0 so that they are displayed only if deduped
with history, shortcut, or bookmark matches.

This CL does not affect how many or which suggestions are displayed. It
only helps format doc suggestions from other providers (e.g. 'Omnibox doc -
01/01/1991 - Google Docs').

Bug: 941548
Change-Id: I173b3f62d3af33f83a6531e086a0ecd0985db986
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1819629Reviewed-by: Tommy Li <tommycli@chromium.org>
Commit-Queue: manuk hovanesian <manukh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#699027}

components/omnibox/browser/document_provider.cc

@@ -695,9 +695,6 @@ ACMatches DocumentProvider::ParseDocumentSearchResults(
   // Ensure server's suggestions are added with monotonically decreasing scores.
   int previous_score = INT_MAX;
   for (size_t i = 0; i < num_results; i++) {
-    if (matches.size() >= provider_max_matches_) {
-      break;
-    }
     const base::DictionaryValue* result = nullptr;
     if (!results_list->GetDictionary(i, &result)) {
       return matches;
@@ -716,25 +713,31 @@ ACMatches DocumentProvider::ParseDocumentSearchResults(
     int server_score = 0;
     result->GetInteger("score", &server_score);
     int score = 0;
-    if (use_client_score && use_server_score)
-      score = std::min(client_score, server_score);
-    else
-      score = use_client_score ? client_score : server_score;
-
-    if (cap_score_per_rank) {
-      int score_cap = i < score_caps.size() ? score_caps[i] : score_caps.back();
-      score = std::min(score, score_cap);
-    }
+    // Set |score| only if we haven't surpassed |provider_max_matches_| yet.
+    // Otherwise, score the remaining matches 0 to avoid displaying them except
+    // when deduped with history, shortcut, or bookmark matches.
+    if (matches.size() < provider_max_matches_) {
+      if (use_client_score && use_server_score)
+        score = std::min(client_score, server_score);
+      else
+        score = use_client_score ? client_score : server_score;
+
+      if (cap_score_per_rank) {
+        int score_cap =
+            i < score_caps.size() ? score_caps[i] : score_caps.back();
+        score = std::min(score, score_cap);
+      }
 
-    if (boost_owned)
-      score = BoostOwned(score, client_->ProfileUserName(), result);
+      if (boost_owned)
+        score = BoostOwned(score, client_->ProfileUserName(), result);
 
-    // Decrement scores if necessary to ensure suggestion order is preserved.
-    // Don't decrement client scores which don't necessarily rank suggestions
-    // the same as the server.
-    if (!use_client_score && score >= previous_score)
-      score = std::max(previous_score - 1, 0);
-    previous_score = score;
+      // Decrement scores if necessary to ensure suggestion order is preserved.
+      // Don't decrement client scores which don't necessarily rank suggestions
+      // the same as the server.
+      if (!use_client_score && score >= previous_score)
+        score = std::max(previous_score - 1, 0);
+      previous_score = score;
+    }
 
     AutocompleteMatch match(this, score, false,
                             AutocompleteMatchType::DOCUMENT_SUGGESTION);
@@ -776,6 +779,8 @@ ACMatches DocumentProvider::ParseDocumentSearchResults(
     match.transition = ui::PAGE_TRANSITION_GENERATED;
     match.RecordAdditionalInfo("client score", client_score);
     match.RecordAdditionalInfo("server score", server_score);
+    if (matches.size() >= provider_max_matches_)
+      match.RecordAdditionalInfo("for deduping only", "true");
     const std::string* snippet = result->FindStringPath("snippet.snippet");
     if (snippet)
       match.RecordAdditionalInfo("snippet", *snippet);