[cros search service] Add case-insensitive exact match to TokenizedStringMatch

We're consolidating exact & fuzzy string match to be both supported by
the search service. In this cl, we add case-insensitive exact match to
TokenizedStringMatch and remove it from app_search_provider. Note, fuzzy
string match already performs case-insensitive exact match internally.

Bug: 1018613
Change-Id: Ia7d17352e3b263ab09fac1e590748a08d7b16eb1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2089534Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Jia Meng <jiameng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#748068}

chrome/browser/ui/app_list/search/app_search_provider.cc

@@ -551,7 +551,6 @@ void AppSearchProvider::UpdateQueriedResults() {
         // Exact matches should be shown even if the threshold isn't reached,
         // e.g. due to a localized name being particularly short.
         if (match.relevance() <= app->relevance_threshold() &&
-            !base::EqualsCaseInsensitiveASCII(query_, app->name()) &&
             !app->MatchSearchableText(query_terms, use_exact_match)) {
           continue;
         }

chrome/common/string_matching/tokenized_string_match.cc

@@ -11,6 +11,7 @@
 #include "base/i18n/string_search.h"
 #include "base/logging.h"
 #include "base/macros.h"
+#include "base/strings/string_util.h"
 #include "chrome/common/string_matching/tokenized_string_char_iterator.h"
 
 namespace {
@@ -195,6 +196,19 @@ bool TokenizedStringMatch::Calculate(const TokenizedString& query,
   relevance_ = kNoMatchScore;
   hits_.clear();
 
+  // If there is an exact match, relevance will be 1.0 and there is only 1 hit
+  // that is the entire text/query.
+  const auto& query_text = query.text();
+  const auto& text_text = text.text();
+  const auto query_size = query_text.size();
+  const auto text_size = text_text.size();
+  if (query_size > 0 && query_size == text_size &&
+      base::EqualsCaseInsensitiveASCII(query_text, text_text)) {
+    hits_.push_back(gfx::Range(0, query_size));
+    relevance_ = 1.0;
+    return true;
+  }
+
   PrefixMatcher matcher(query, text);
   if (matcher.Match()) {
     relevance_ = matcher.relevance();