[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}
bool ContextualSearchFieldTrial::IsDecodeMentionsDisabled() {
  return GetBooleanParam(kContextualSearchDecodeMentionsDisabledParamName,
                         &is_decode_mentions_disabled_cached_,
                          &is_decode_mentions_disabled_);
 }

bool ContextualSearchFieldTrial::IsDecodeMentionsDisabled() {
  return GetBooleanParam(kContextualSearchDecodeMentionsDisabledParamName,
                         &is_decode_mentions_disabled_cached_,
                          &is_decode_mentions_disabled_);
 }
