[Contextual Search] Change "Now on Tap" to "Contextual Cards"

BUG=644934

Review-Url: https://codereview.chromium.org/2361163003
Cr-Commit-Position: refs/heads/master@{#420899}
base::string16 TemplateURL::GenerateKeyword(const GURL& url) {
  DCHECK(url.is_valid());
  base::string16 keyword = url_formatter::StripWWW(
      url_formatter::IDNToUnicode(url.host()));
  return keyword.empty() ? base::ASCIIToUTF16("www") : keyword;
}

base::string16 TemplateURL::GenerateKeyword(const GURL& url) {
  DCHECK(url.is_valid());
  base::string16 keyword = url_formatter::StripWWW(
      url_formatter::IDNToUnicode(url.host()));
  return keyword.empty() ? base::ASCIIToUTF16("www") : keyword;
}
