populateUi_() {
    goog.Promise
        .all([
          // Populate the UI with the available encryption keys.
          this.renderEncryptionKeys_(),
          // Populate the UI with the available signing keys.
          this.renderSigningKeys_(),
          // Load selected content.
          this.loadSelectedContent_()
        ])
        .then(
            // When all of the above steps completed, set up focus.
            this.focusRelevantElement_, undefined, this);
  }
Populates the UI elements with the received data.
@private