code: function() {
      this.setHelpUrl(Blockly.Msg.CONTROLS_IF_HELPURL);
      this.setColour(Blockly.Blocks.logic.HUE);
      this.appendValueInput('IF0')
          .setCheck('Boolean')
          .appendField(Blockly.Msg.CONTROLS_IF_MSG_IF);
      this.appendStatementInput('DO0')
          .appendField(Blockly.Msg.CONTROLS_IF_MSG_THEN);
      this.setPreviousStatement(true);
      this.setNextStatement(true);
      this.setMutator(new Blockly.Mutator(['controls_if_elseif',
                                           'controls_if_else']));
      // Assign 'this' to a variable for use in the tooltip closure below.
      var thisBlock = this;
      this.setTooltip(function() {
        if (!thisBlock.elseifCount_ && !thisBlock.elseCount_) {
          return Blockly.Msg.CONTROLS_IF_TOOLTIP_1;
        } else if (!thisBlock.elseifCount_ && thisBlock.elseCount_) {
          return Blockly.Msg.CONTROLS_IF_TOOLTIP_2;
        } else if (thisBlock.elseifCount_ && !thisBlock.elseCount_) {
          return Blockly.Msg.CONTROLS_IF_TOOLTIP_3;
        } else if (thisBlock.elseifCount_ && thisBlock.elseCount_) {
          return Blockly.Msg.CONTROLS_IF_TOOLTIP_4;
        }
        return '';
      });
      this.elseifCount_ = 0;
      this.elseCount_ = 0;
    }
docs: Block for if/elseif/else condition.
  @this Blockly.Block