[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}
void TemplateURL::InvalidateCachedValues() const {
  for (const TemplateURLRef& ref : url_refs_)
    ref.InvalidateCachedValues();
  suggestions_url_ref_.InvalidateCachedValues();
  instant_url_ref_.InvalidateCachedValues();
  image_url_ref_.InvalidateCachedValues();
  new_tab_url_ref_.InvalidateCachedValues();
  contextual_search_url_ref_.InvalidateCachedValues();
}

void TemplateURL::InvalidateCachedValues() const {
  for (const TemplateURLRef& ref : url_refs_)
    ref.InvalidateCachedValues();
  suggestions_url_ref_.InvalidateCachedValues();
  instant_url_ref_.InvalidateCachedValues();
  image_url_ref_.InvalidateCachedValues();
  new_tab_url_ref_.InvalidateCachedValues();
  contextual_search_url_ref_.InvalidateCachedValues();
}
