Revert "[omnibox] Fix ZeroSuggestProvider duplicate classifications bug"

This reverts commit ebc60412.

Reason for revert: Broke compile on iOS
https://ci.chromium.org/p/chromium/builders/ci/ios-device/143201

Original change's description:
> [omnibox] Fix ZeroSuggestProvider duplicate classifications bug
> 
> The below CL introduces a bug, where ZeroSuggestProvider can create
> a match with duplicate text classifications. This triggers a DCHECK
> as described in the linked bug.
> 
> https://chromium-review.googlesource.com/c/chromium/src/+/1947765
> 
> This CL fixes it and adds a test.
> 
> Bug: 1030741
> Change-Id: If59fbd320d720e2a7ff8d2f66d9ee92e11bb9a68
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1951557
> Commit-Queue: Tommy Li <tommycli@chromium.org>
> Reviewed-by: manuk hovanesian <manukh@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#722497}

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

Change-Id: Idba8826447487022b4149a310bdb67e8ae560268
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1030741
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1954941Reviewed-by: Aaron Gable <agable@chromium.org>
Commit-Queue: Aaron Gable <agable@chromium.org>
Cr-Commit-Position: refs/heads/master@{#722501}

components/omnibox/browser/search_suggestion_parser.cc

@@ -149,15 +149,12 @@ operator=(const SuggestResult& rhs) = default;
 void SearchSuggestionParser::SuggestResult::ClassifyMatchContents(
     const bool allow_bolding_all,
     const base::string16& input_text) {
-  // Start with the trivial nothing-bolded classification.
-  DCHECK(!match_contents_.empty());
-  match_contents_class_.clear();
-  match_contents_class_.push_back(
-      ACMatchClassification(0, ACMatchClassification::NONE));
-
-  // Leave trivial classification alone in the ZeroSuggest case.
-  if (input_text.empty())
+  if (input_text.empty()) {
+    // In case of zero-suggest results, do not highlight matches.
+    match_contents_class_.push_back(
+        ACMatchClassification(0, ACMatchClassification::NONE));
     return;
+  }
 
   base::string16 lookup_text = input_text;
   if (type_ == AutocompleteMatchType::SEARCH_SUGGEST_TAIL) {
@@ -184,7 +181,6 @@ void SearchSuggestionParser::SuggestResult::ClassifyMatchContents(
     return;
   }
 
-  // Note we discard our existing match_contents_class_ with this call.
   match_contents_class_ = AutocompleteProvider::ClassifyAllMatchesInString(
       input_text, match_contents_, true);
 }
@@ -248,15 +244,12 @@ void
 SearchSuggestionParser::NavigationResult::CalculateAndClassifyMatchContents(
     const bool allow_bolding_nothing,
     const base::string16& input_text) {
-  // Start with the trivial nothing-bolded classification.
-  DCHECK(url_.is_valid());
-  match_contents_class_.clear();
-  match_contents_class_.push_back(
-      ACMatchClassification(0, ACMatchClassification::NONE));
-
-  // Leave trivial classification alone in the ZeroSuggest case.
-  if (input_text.empty())
+  if (input_text.empty()) {
+    // In case of zero-suggest results, do not highlight matches.
+    match_contents_class_.push_back(
+        ACMatchClassification(0, ACMatchClassification::NONE));
     return;
+  }
 
   // Set contents to the formatted URL while ensuring the scheme and subdomain
   // are kept if the user text seems to include them. E.g., for the user text

components/omnibox/browser/search_suggestion_parser_unittest.cc

@@ -7,7 +7,6 @@
 #include "base/json/json_reader.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/values.h"
-#include "components/omnibox/browser/autocomplete_match.h"
 #include "components/omnibox/browser/test_scheme_classifier.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ -155,32 +154,3 @@ TEST(SearchSuggestionParserTest, ParseSuggestResults) {
     ASSERT_EQ("http://example.com/a.png", suggestion_result.image_url());
   }
 }
-
-TEST(SearchSuggestionParserTest, SuggestClassification) {
-  AutocompleteMatch::ACMatchClassification none_classification(
-      0, AutocompleteMatch::ACMatchClassification::NONE);
-
-  SearchSuggestionParser::SuggestResult result(
-      base::ASCIIToUTF16("foobar"), AutocompleteMatchType::SEARCH_SUGGEST, 0,
-      false, 400, true, base::string16());
-  AutocompleteMatch dummy_match;
-  dummy_match.ValidateClassifications(result.match_contents(),
-                                      result.match_contents_class());
-
-  // Re-classify the match contents, as the ZeroSuggestProvider does.
-  result.ClassifyMatchContents(true, base::string16());
-  dummy_match.ValidateClassifications(result.match_contents(),
-                                      result.match_contents_class());
-
-  // Make sure that searching text-not-found still gives valid classifications,
-  // if we don't allow the code to bold everything.
-  result.ClassifyMatchContents(false, base::ASCIIToUTF16("apple"));
-  dummy_match.ValidateClassifications(result.match_contents(),
-                                      result.match_contents_class());
-
-  // Make sure that searching text-not-found still gives valid classifications,
-  // if we don't allow the code to bold everything.
-  result.ClassifyMatchContents(true, base::ASCIIToUTF16("foobar"));
-  dummy_match.ValidateClassifications(result.match_contents(),
-                                      result.match_contents_class());
-}
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