Add "MkKeyContext" KeyContext generation function.

filter/txnBuf/txnbuf_test.go

 // Copyright 2015 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package txnBuf
 
 import (
         "bytes"
         "fmt"
         "math/rand"
@@ skipping 76 matching lines @@
                 }
                 return ShouldBeNil(ds.Put(c, f))
         }
 }
 
 var (
         dataMultiRoot  = make([]*Foo, 20)
         dataSingleRoot = make([]*Foo, 20)
         hugeField      = make([]byte, DefaultSizeBudget/8)
         hugeData       = make([]*Foo, 11)
-        root           = ds.KeyContext{"something~else", ""}.MakeKey("Parent", 1)
+        root           = ds.MkKeyContext("something~else", "").MakeKey("Parent", 1)
 )
 
 func init() {
         cb := func(i int64) string {
                 buf := &bytes.Buffer{}
                 cmpbin.WriteInt(buf, i)
                 return buf.String()
         }
 
         rs := rand.NewSource(0)
@@ skipping 747 matching lines @@
                                         val := pm.Slice("Value")
                                         So(val[len(val)-1].Value(), ShouldResemble, "wat")
                                 }), ShouldBeNil)
                         })
 
                 })
 
         })
 
 }