more consistent private properties naming

src/directives/public/for.js

@@ -309,7 +309,7 @@ const vFor = {
       var anchor = frag.staggerAnchor
       if (!anchor) {
         anchor = frag.staggerAnchor = createAnchor('stagger-anchor')
-        anchor.__vfrag__ = frag
+        anchor.__v_frag = frag
       }
       after(anchor, prevEl)
       var op = frag.staggerCb = cancellable(function () {
@@ -575,7 +575,7 @@ function findPrevFrag (frag, anchor, id) {
   var el = frag.node.previousSibling
   /* istanbul ignore if */
   if (!el) return
-  frag = el.__vfrag__
+  frag = el.__v_frag
   while (
     (!frag || frag.forId !== id || !frag.inserted) &&
     el !== anchor
@@ -583,7 +583,7 @@ function findPrevFrag (frag, anchor, id) {
     el = el.previousSibling
     /* istanbul ignore if */
     if (!el) return
-    frag = el.__vfrag__
+    frag = el.__v_frag
   }
   return frag
 }

src/fragment/fragment.js

@@ -37,7 +37,7 @@ export default function Fragment (linker, vm, frag, host, scope, parentFrag) {
   var single = this.single =
     frag.childNodes.length === 1 &&
     // do not go single mode if the only node is an anchor
-    !(frag.childNodes[0].__vue_anchor)
+    !(frag.childNodes[0].__v_anchor)
   if (single) {
     this.node = frag.childNodes[0]
     this.before = singleBefore
@@ -51,7 +51,7 @@ export default function Fragment (linker, vm, frag, host, scope, parentFrag) {
     this.before = multiBefore
     this.remove = multiRemove
   }
-  this.node.__vfrag__ = this
+  this.node.__v_frag = this
 }
 
 /**
@@ -181,7 +181,7 @@ Fragment.prototype.destroy = function () {
   if (this.parentFrag) {
     this.parentFrag.childFrags.$remove(this)
   }
-  this.node.__vfrag__ = null
+  this.node.__v_frag = null
   this.unlink()
 }
 

src/util/dom.js

@@ -330,7 +330,7 @@ export function createAnchor (content, persist) {
   var anchor = config.debug
     ? document.createComment(content)
     : document.createTextNode(persist ? ' ' : '')
-  anchor.__vue_anchor = true
+  anchor.__v_anchor = true
   return anchor
 }