Revert "[omnibox] Dedup history matches HQP matches."

This reverts commit 14f12b97.

Reason for revert: As mpearson pointed out, this CL has an unintended affect on HQP suggestions.

This is a partial revert. A full revert would fail tests due to other
changes since the original CL landed. This revert keeps test changes
from the original CL and updates another test. Additionally, it retains
a variable rename and formatting change since those have no functional
effect and we prefer the newer versions.

Original change's description:
> [omnibox] Dedup history matches HQP matches.
>
> This CL filters duplicate history matches in
> URLIndexPrivateData::HistoryItemsForTerms used by the HQP. Previously,
> we relied on the autocomplete controller's deduping which
> 1) may affect performance since it occured after additional processing
> of each suggestion (I would guess it's insignificant), and
> 2) prevented the HQP provider from making full use of it's allocated
> per-provider-limit.
>
> Also update a few HQP unit tests.
>
> Bug: 591981
> Change-Id: I1c6ce02050ba1b674e3507368c1a095f5a5b0c6d
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2219027
> Commit-Queue: manuk hovanesian <manukh@chromium.org>
> Reviewed-by: Tommy Li <tommycli@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#773185}

TBR=tommycli@chromium.org,jdonnelly@chromium.org,manukh@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 591981
Change-Id: I00ad1ebdcb40163b0eb488dd5771f1b703566aeb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2327955Reviewed-by: Mark Pearson <mpearson@chromium.org>
Reviewed-by: manuk hovanesian <manukh@chromium.org>
Reviewed-by: Justin Donnelly <jdonnelly@chromium.org>
Reviewed-by: Tommy Li <tommycli@chromium.org>
Commit-Queue: manuk hovanesian <manukh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#796553}

components/omnibox/browser/history_quick_provider_unittest.cc

@@ -407,11 +407,11 @@ TEST_F(HistoryQuickProviderTest, SingleMatchWithCursor) {
 TEST_F(HistoryQuickProviderTest, MatchWithAndWithoutCursorWordBreak) {
   std::vector<std::string> expected_urls;
   expected_urls.push_back("https://twitter.com/fungoodtimes");
-  // With cursor after "good", we should retrieve the desired result but it
+  // With cursor after ".com", we should retrieve the desired result but it
   // should not be allowed to be the default match.
-  RunTestWithCursor(ASCIIToUTF16("fungoodtimes"), 7, false, expected_urls,
-                    false, ASCIIToUTF16("https://twitter.com/fungoodtimes"),
-                    base::string16());
+  RunTestWithCursor(
+      ASCIIToUTF16("twitter.comfungoodtimes"), 11, false, expected_urls, false,
+      ASCIIToUTF16("https://twitter.com/fungoodtimes"), base::string16());
 }
 
 TEST_F(HistoryQuickProviderTest, WordBoundariesWithPunctuationMatch) {

components/omnibox/browser/url_index_private_data.cc

@@ -185,8 +185,6 @@ ScoredHistoryMatches URLIndexPrivateData::HistoryItemsForTerms(
   // A set containing the list of words extracted from each search string,
   // used to prevent running duplicate searches.
   std::set<String16Vector> seen_search_words;
-  // Likewise, a set of seen history_ids to prevent creating duplicate matches.
-  std::set<HistoryID> seen_history_ids;
   for (const base::string16& search_string : search_strings) {
     // The search string we receive may contain escaped characters. For reducing
     // the index we need individual, lower-cased words, ignoring escapings. For
@@ -215,14 +213,6 @@ ScoredHistoryMatches URLIndexPrivateData::HistoryItemsForTerms(
     seen_search_words.insert(lower_words);
 
     HistoryIDVector history_ids = HistoryIDsFromWords(lower_words);
-    // Filter history IDs found previously. Otherwise, we'll end up creating and
-    // pushing duplicate matches into |scored_items|. Besides being wasteful,
-    // this could result in not making full use of max_matches.
-    base::EraseIf(history_ids, [seen_history_ids](const auto& history_id) {
-      return seen_history_ids.count(history_id);
-    });
-    seen_history_ids.insert(history_ids.begin(), history_ids.end());
-
     history_ids_were_trimmed |= TrimHistoryIdsPool(&history_ids);
 
     HistoryIdsToScoredMatches(std::move(history_ids), lower_raw_string,