Provide the equivalent of GURL::DomainIs for url::Origin.

url/url_util.cc

Index: url/url_util.cc
diff --git a/url/url_util.cc b/url/url_util.cc
index c1e997992d3569496b96e64014a79e692bc01bcf..9322d9606a5e16b2b54a5ac6c40024966129b8e5 100644
--- a/url/url_util.cc
+++ b/url/url_util.cc
@@ -616,6 +616,43 @@ void EncodeURIComponent(const char* input, int length, CanonOutput* output) {
   }
 }
 
+bool DomainIs(base::StringPiece canonicalized_host,
+              base::StringPiece lower_ascii_domain) {
+  DCHECK(!canonicalized_host.empty());

[engedy, 2016/08/26 16:48:14]

I think it would be safer if this shared stuff did the checking, and returned
false if either argument is the empty string.

Then we could get rid of the checking in the two places that call into this. 

Don't forget to add the new unittests in URLUtils.

[pkalinnikov, 2016/08/29 09:53:00]

Done.

+  DCHECK(!lower_ascii_domain.empty());
+
+  // If the host name ends with a dot but the input domain doesn't, then we
+  // ignore the dot in the host name.
+  size_t host_len = canonicalized_host.length();
+  if (canonicalized_host.back() == '.' && lower_ascii_domain.back() != '.')
+    --host_len;
+
+  if (host_len < lower_ascii_domain.length())
+    return false;
+
+  // |host_first_pos| is the start of the compared part of the host name, not
+  // start of the whole host name.
+  const char* host_first_pos =
+      canonicalized_host.data() + host_len - lower_ascii_domain.length();
+
+  if (!base::LowerCaseEqualsASCII(
+          base::StringPiece(host_first_pos, lower_ascii_domain.length()),
+          lower_ascii_domain)) {
+    return false;
+  }
+
+  // Make sure there aren't extra characters in host before the compared part;
+  // if the host name is longer than the input domain name, then the character
+  // immediately before the compared part should be a dot. For example,
+  // www.google.com has domain "google.com", but www.iamnotgoogle.com does not.
+  if (lower_ascii_domain[0] != '.' && host_len > lower_ascii_domain.length() &&
+      *(host_first_pos - 1) != '.') {
+    return false;
+  }
+
+  return true;
+}
+
 bool CompareSchemeComponent(const char* spec,
                             const Component& component,
                             const char* compare_to) {