Use entrance counter instead of flag

Per discussions in #473 (comment); this is alternative (A)

source

@@ -87435,8 +87435,8 @@ interface <dfn>NavigatorOnLine</dfn> {
 
   <ol>
 
-   <li><p>Set <var>settings</var>'s <span>realm execution context</span>'s <span>is candidate entry
-   execution context</span> flag.</p></li>
+   <li><p>Increment <var>settings</var>'s <span>realm execution context</span>'s <span>entrance
+   counter</span> by one.</p></li>
 
    <li><p>Push <var>settings</var>'s <span>realm execution context</span> onto the <span>JavaScript
    execution context stack</span>; it is now the <span>running JavaScript execution
@@ -87453,8 +87453,8 @@ interface <dfn>NavigatorOnLine</dfn> {
    <li><p>Assert: <var>settings</var>'s <span>realm execution context</span> is the <span>running
    JavaScript execution context</span>.</p></li>
 
-   <li><p>Unset <var>settings</var>'s <span>realm execution context</span>'s <span>is candidate
-   entry execution context</span> flag.</p></li>
+   <li><p>Decrement <var>settings</var>'s <span>realm execution context</span>'s <span>entrance
+   counter</span> by one.</p></li>
 
    <li><p>Remove <var>settings</var>'s <span>realm execution context</span> from the
    <span>JavaScript execution context stack</span>.</p></li>
@@ -87486,7 +87486,7 @@ interface <dfn>NavigatorOnLine</dfn> {
   perform each of the jobs in the <span>global script clean-up jobs list</span> and then empty the
   list.</p>
 
-  <h5>Realms, settings objects, and global objects</h5>
+  <h5 id="realms-settings-objects-global-objects">Realms, settings objects, and global objects</h5>
 
   <p>A <dfn>global object</dfn> is a JavaScript object that is the [[GlobalObject]] field of a
   <span>JavaScript realm</span>.</p>
@@ -87692,15 +87692,15 @@ interface <dfn>NavigatorOnLine</dfn> {
 
   <h6>Entry</h6>
 
-  <p>All <span data-x="JavaScript execution context">JavaScript execution contexts</span> must
-  contain, as part of their code evaluation state, an <dfn>is candidate entry execution
-  context</dfn> flag, which is initially unset. In the process of <a href="#calling-scripts">calling
-  scripts</a>, this flag will be toggled.</p>
+  <p>All <span data-x="realm execution context">realm execution contexts</span> must contain, as
+  part of their code evaluation state, an <dfn>entrance counter</dfn> value, which is initially
+  zero. In the process of <a href="#calling-scripts">calling scripts</a>, this value will be
+  incremented and decremented.</p>
 
   <p>With this in hand, we define the <dfn>entry execution context</dfn> to be the most recently
-  pushed entry in the <span>JavaScript execution context stack</span> whose <span>is candidate entry
-  execution context</span> flag is set to true. The <dfn data-x="concept-entry-realm">entry
-  Realm</dfn> is the <span>entry execution context</span>'s Realm component.</p>
+  pushed entry in the <span>JavaScript execution context stack</span> whose <span>entrance
+  counter</span> value is greater than zero. The <dfn data-x="concept-entry-realm">entry Realm</dfn>
+  is the <span>entry execution context</span>'s Realm component.</p>
 
   <p>Then, the <dfn>entry settings object</dfn> is the <span
   data-x="concept-realm-settings-object">environment settings object</span> of the <span