strip origin when normalizing base (#1448)

fix #1426

Author: sabakugaara

src/history/base.js

@@ -188,11 +188,14 @@ export class History {
 }
 
 function normalizeBase (base: ?string): string {
+  // respect <base> tag
   if (!base) {
     if (inBrowser) {
       // respect <base> tag
-      const baseEl = document.querySelector('base')
-      base = (baseEl && baseEl.getAttribute('href')) || '/'
+      const baseURI = document.baseURI || '/'
+      const a = document.createElement('a')
+      a.href = baseURI
+      base = a.pathname
     } else {
       base = '/'
     }