Replace mph.json file with country-coder implementation (re: #6941)

data/index.js

@@ -10,7 +10,6 @@ export { dataShortcuts } from './shortcuts.json';
 export { dataTerritoryLanguages } from './territory-languages.json';
 
 export { default as dataImperial } from './imperial.json';
-export { default as dataMPH } from './mph.json';
 export { default as dataDriveLeft } from './drive-left.json';
 export { en as dataEn } from '../dist/locales/en.json';
 

modules/ui/fields/maxspeed.js

@@ -1,8 +1,7 @@
 import { dispatch as d3_dispatch } from 'd3-dispatch';
 import { select as d3_select } from 'd3-selection';
+import * as countryCoder from 'country-coder';
 
-import { dataMPH } from '../../../data';
-import { geoPointInPolygon } from '../../geo';
 import { uiCombobox } from '../combobox';
 import { utilGetSetValue, utilNoAuto, utilRebind } from '../../util';
 
@@ -57,11 +56,7 @@ export function uiFieldMaxspeed(field, context) {
             loc = childNodes[~~(childNodes.length/2)].loc;
         }
 
-        _isImperial = dataMPH.features.some(function(f) {
-            return f.geometry.coordinates.some(function(d) {
-                return geoPointInPolygon(loc, d);
-            });
-        });
+        _isImperial = countryCoder.roadSpeedUnit(loc) === 'mph';
 
         unitInput = wrap.selectAll('input.maxspeed-unit')
             .data([0]);