extract overlay class name into constant

ui/src/data_explorer/components/WriteDataForm.js

@@ -2,6 +2,7 @@ import React, {Component, PropTypes} from 'react'
 
 import DatabaseDropdown from 'shared/components/DatabaseDropdown'
 import OnClickOutside from 'shared/components/OnClickOutside'
+import {OVERLAY_CLASS} from 'shared/constants'
 
 class WriteDataForm extends Component {
   constructor(props) {
@@ -24,7 +25,7 @@ class WriteDataForm extends Component {
 
   handleClickOutside(e) {
     // guard against clicking to close error notification
-    if (e.target.className === 'overlay-technology') {
+    if (e.target.className === OVERLAY_CLASS) {
       const {onClose} = this.props
       onClose()
     }

ui/src/shared/components/OverlayTechnologies.js

@@ -1,7 +1,9 @@
 import React, {PropTypes} from 'react'
 
+import {OVERLAY_CLASS} from 'shared/constants'
+
 const OverlayTechnologies = ({children}) => (
-  <div className="overlay-technology">{children}</div>
+  <div className={OVERLAY_CLASS}>{children}</div>
 )
 
 const {node} = PropTypes

ui/src/shared/constants/index.js

@@ -399,3 +399,5 @@ export const AUTOREFRESH_DEFAULT = 15000 // in milliseconds
 export const GRAPH = 'graph'
 export const TABLE = 'table'
 export const VIS_VIEWS = [GRAPH, TABLE]
+
+export const OVERLAY_CLASS = 'overlay-technology'