[Omnibox] Avoid removing the `www.` prefix during deduping when doing so would...

[Omnibox] Avoid removing the `www.` prefix during deduping when doing so would leave no host component.

When sorting and deduping matches, match GURLs are stripped (`AutocompleteMatch::GURLToStrippedGURL`). Certain omnibox inputs, such as `http://www.` without inline autocomplete, produce matches with host compoments `www.`. Stripping `www.` in these cases would result in an empty url host component and, therefore, invalid `GURL`. Invoking `GURL::spec` on such invalid URLs would then cause a DCHECK to evaluate false and crash the browser. The crash only affects debug builds as the DCHECK is inactive for non-debug builds.

Bug: 898554
Change-Id: I73461c65ba53891d6f3b52bc767c754b02c1ce3e
Reviewed-on: https://chromium-review.googlesource.com/c/1331631
Commit-Queue: manuk hovanesian <manukh@chromium.org>
Reviewed-by: Tommy Li <tommycli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607709}

components/omnibox/browser/autocomplete_match.cc

@@ -521,7 +521,7 @@ GURL AutocompleteMatch::GURLToStrippedGURL(
   static const char prefix[] = "www.";
   static const size_t prefix_len = arraysize(prefix) - 1;
   std::string host = stripped_destination_url.host();
-  if (host.compare(0, prefix_len, prefix) == 0) {
+  if (host.compare(0, prefix_len, prefix) == 0 && host.length() > prefix_len) {
     replacements.SetHostStr(base::StringPiece(host).substr(prefix_len));
     needs_replacement = true;
   }

components/omnibox/browser/autocomplete_match_unittest.cc

@@ -374,6 +374,9 @@ TEST(AutocompleteMatchTest, Duplicates) {
                           "https://xn--1lq90ic7f1rc.cn/", false },
     { L"http://\x89c6 x", "http://xn--1lq90ic7f1rc.cn/",
                           "https://xn--1lq90ic7f1rc.cn/", true  },
+
+    // URLs with hosts containing only `www.` should produce valid stripped urls
+    { L"http://www./", "http://www./", "http://google.com/", false },
   };
 
   for (size_t i = 0; i < arraysize(cases); ++i) {
@@ -392,5 +395,7 @@ TEST(AutocompleteMatchTest, Duplicates) {
     m2.ComputeStrippedDestinationURL(input, nullptr);
     EXPECT_EQ(cases[i].expected_duplicate,
               m1.stripped_destination_url == m2.stripped_destination_url);
+    EXPECT_TRUE(m1.stripped_destination_url.is_valid());
+    EXPECT_TRUE(m2.stripped_destination_url.is_valid());
   }
 }