arations.findIndex(p => p.name === name);
  }

  /**
   * Sets a number of properties on the node.
   *
   * @param  {Array} properties
   *         An array of properties, each is an object with name and
   *         value properties. If the value is "" then the property
   *         is removed.
   * @return {Promise} Resolves when the modifications are complete.
   */
  async setProperties(properties) {
    for (const property of properties) {
      // Get a RuleModificationList or RuleRewriter helper object from the
      // StyleRuleActor to make changes to CSS properties.
      // Note that RuleRewriter doesn't support modifying several properties at
      // once, so we do this in a sequence here.
      const modifications = this._rules[0].startModifyingProperties(
        this._inspector.panelWin,
        this._inspector.cssProperties
      );

      // Remember the property so it can be reverted.
      if (!this._modifications.has(property.name)) {
        this._modifications.set(
          property.name,
          this.getPropertyFromRule(this._rules[0], property.name)
        );
      }

      // Find the index of the property to be changed, or get the next index to
      // insert the new property at.
      let index = this.getPropertyIndex(property.name);
      if (index === -1) {
        index = this._rules[0].declarations.length;
      }

      if (property.value == "") {
        modifications.removeProperty(index, property.name);
      } else {
        modifications.setProperty(index, property.name, property.value, "");
      }

      await modifications.apply();
    }
  }

  /**
   * Reverts all of the property changes made by this instance.
   *
   * @return {Promise} Resolves when all properties have been reverted.
   */
  async revert() {
    // Revert each property that we modified previously, one by one. See
    // setProperties for information about why.
    for (const [property, value] of this._modifications) {
      const modifications = this._rules[0].startModifyingProperties(
        this._inspector.panelWin,
        this._inspector.cssProperties
      );

      // Find the index of the property to be reverted.
      let index = this.getPropertyIndex(property);

      if (value != "") {
        // If the property doesn't exist anymore, insert at the beginning of the
        // rule.
        if (index === -1) {
          index = 0;
        }
        modifications.setProperty(index, property, value, "");
      } else {
        // If the property doesn't exist anymore, no need to remove it. It had
        // not been added after all.
        if (index === -1) {
          continue;
        }
        modifications.removeProperty(index, property);
      }

      await modifications.apply();
    }
  }

  destroy() {
    this._modifications.clear();

    this._cssProperties = null;
    this._doc = null;
    this._inspector = null;
    this._modifications = null;
    this._rules = null;
  }
}

module.exports = EditingSession;
PK