Return if a host name in an URLPattern has no non-whitespace characters.

extensions/common/url_pattern.cc

Index: extensions/common/url_pattern.cc
diff --git a/extensions/common/url_pattern.cc b/extensions/common/url_pattern.cc
index c7a3711e039fee6a7eb5b0f1c79ea7e111b2dd3f..6eb6c8c2c17c9912376cc2858dc09cec788d4f11 100644
--- a/extensions/common/url_pattern.cc
+++ b/extensions/common/url_pattern.cc
@@ -219,6 +219,11 @@ URLPattern::ParseResult URLPattern::Parse(const std::string& pattern) {
     // The first component can optionally be '*' to match all subdomains.
     std::vector<std::string> host_components;
     base::SplitString(host_, '.', &host_components);
+
+    // Could be empty if the host only consists of whitespace characters.
+    if (host_components.empty())
+      return PARSE_ERROR_EMPTY_HOST;
+
     if (host_components[0] == "*") {
       match_subdomains_ = true;
       host_components.erase(host_components.begin(),