Make take()/drop() not share state across calls (#155)

spec.bs

@@ -770,8 +770,9 @@ For now, see [https://github.com/wicg/observable#operators](https://github.com/w
 
     1. Let |observable| be a [=new=] {{Observable}} whose [=Observable/subscribe callback=] is an
        algorithm that takes a {{Subscriber}} |subscriber| and does the following:
+       1. Let |remaining| be |amount|.
 
-       1. If |amount| is 0, then run |subscriber|'s {{Subscriber/complete()}} method and abort
+       1. If |remaining| is 0, then run |subscriber|'s {{Subscriber/complete()}} method and abort
           these steps.
 
        1. Let |sourceObserver| be a new [=internal observer=], initialized as follows:
@@ -780,9 +781,9 @@ For now, see [https://github.com/wicg/observable#operators](https://github.com/w
           :: 1. Run |subscriber|'s {{Subscriber/next()}} method with the passed in <var
                 ignore>value</var>.
 
-             1. Decrement |amount|.
+             1. Decrement |remaining|.
 
-             1. If |amount| is 0, then run |subscriber|'s {{Subscriber/complete()}} method.
+             1. If |remaining| is 0, then run |subscriber|'s {{Subscriber/complete()}} method.
 
           : [=internal observer/error steps=]
           :: Run |subscriber|'s {{Subscriber/error()}} method, given the passed in <var
@@ -811,13 +812,14 @@ For now, see [https://github.com/wicg/observable#operators](https://github.com/w
 
     1. Let |observable| be a [=new=] {{Observable}} whose [=Observable/subscribe callback=] is an
        algorithm that takes a {{Subscriber}} |subscriber| and does the following:
+       1. Let |remaining| be |amount|.
 
        1. Let |sourceObserver| be a new [=internal observer=], initialized as follows:
 
           : [=internal observer/next steps=]
-          :: 1. If |amount| is &gt; 0, then decrement |amount| and abort these steps.
+          :: 1. If |remaining| is &gt; 0, then decrement |remaining| and abort these steps.
 
-             1. [=Assert=]: |amount| is 0.
+             1. [=Assert=]: |remaining| is 0.
 
              1. Run |subscriber|'s {{Subscriber/next()}} method with the passed in <var
                 ignore>value</var>.