URL Formatter: Add StripSubdomain method that preserves eTLD + 1.

components/url_formatter/url_formatter_unittest.cc

Index: components/url_formatter/url_formatter_unittest.cc
diff --git a/components/url_formatter/url_formatter_unittest.cc b/components/url_formatter/url_formatter_unittest.cc
index 544f55080a4c6eb940f53e55082d9db2e0346762..e768677700d3f93ad061894e71083dd4a22e951f 100644
--- a/components/url_formatter/url_formatter_unittest.cc
+++ b/components/url_formatter/url_formatter_unittest.cc
@@ -1223,6 +1223,49 @@ TEST(UrlFormatterTest, FormatUrlWithOffsets) {
                        net::UnescapeRule::NORMAL, omit_all_offsets);
 }
 
+TEST(UrlFormatterTest, StripSubdomains) {
+  struct TestCase {
+    std::string expected;
+    std::string input_host;
+    StripSubdomainTypes subdomains_to_strip;
+  } cases[] = {
+      // Test successful strippings of subdomains.
+      {"google.com", "www.google.com", kStripWWW},
+      {"google.com", "m.google.com", kStripM},
+      {"google.com", "www.google.com", kStripWWW | kStripM},
+      {"google.com", "m.google.com", kStripWWW | kStripM},
+      {"google.com", "www.m.google.com", kStripWWW | kStripM},
+      {"google.com", "m.www.google.com", kStripWWW | kStripM},
+
+      // Test partial strippings.
+      {"m.google.com", "www.m.google.com", kStripWWW},
+      {"www.google.com", "m.www.google.com", kStripM},
+      {"en.wikipedia.org", "en.m.wikipedia.org", kStripWWW | kStripM},
+      {"foo.google.com", "www.foo.google.com", kStripWWW | kStripM},
+      {"foo.google.com", "foo.www.google.com", kStripWWW | kStripM},
+
+      // Leave subdomains alone if the flags specify it as such.
+      {"www.google.com", "www.google.com", kStripM},
+      {"m.google.com", "m.google.com", kStripWWW},
+
+      // Leave eTLD+1s (registry and domain) alone.
+      {"google.com", "google.com", kStripWWW},
+      {"www.com", "www.com", kStripWWW | kStripM},
+      {"m.com", "m.com", kStripWWW | kStripM},
+      {"mail.google.com", "mail.google.com", kStripWWW | kStripM},
+      {"www.co.uk", "www.co.uk", kStripWWW},
+      {"www.garden", "www.garden", kStripWWW},
+  };
+
+  for (TestCase& test_case : cases) {
+    EXPECT_EQ(test_case.expected, url_formatter::StripSubdomains(
+                                      GURL("http://" + test_case.input_host),
+                                      test_case.subdomains_to_strip))
+        << "  input_host = " << test_case.input_host << std::endl
+        << "  subdomains_to_strip = " << test_case.subdomains_to_strip;
+  }
+}
+
 }  // namespace
 
 }  // namespace url_formatter