--- a/js/src/vm/EnvironmentObject.h
+++ b/js/src/vm/EnvironmentObject.h
@@ -173,67 +173,83 @@ EnvironmentCoordinateFunctionScript(JSSc
  *    Does not hold 'var' bindings.
  *
  * The embedding (Gecko) uses non-syntactic envs for various things, some of
  * which are detailed below. All env chain listings below are, from top to
  * bottom, outermost to innermost.
  *
  * A. Component loading
  *
- * Components may be loaded in "reuse loader global" mode, where to save on
- * memory, all JSMs and JS-implemented XPCOM modules are loaded into a single
- * global. Each individual JSMs are compiled as functions with their own
- * FakeBackstagePass. They have the following env chain:
+ * Components may be loaded in a shared global mode where most JSMs share a
+ * single global in order to save on memory and avoid CCWs. To support this, a
+ * NonSyntacticVariablesObject is used for each JSM to provide a basic form of
+ * isolation. They have the following env chain:
  *
  *   BackstagePass global
  *       |
- *   Global lexical scope
+ *   LexicalEnvironmentObject[this=global]
  *       |
- *   WithEnvironmentObject wrapping FakeBackstagePass
+ *   NonSyntacticVariablesObject
  *       |
- *   LexicalEnvironmentObject
+ *   LexicalEnvironmentObject[this=nsvo]
  *
- * B. Subscript loading
+ * B.1 Subscript loading
  *
- * Subscripts may be loaded into a target object. They have the following
- * env chain:
+ * Subscripts may be loaded into a target object and it's associated global.
+ * They have the following env chain:
  *
- *   Loader global
+ *   Target object's global
  *       |
- *   Global lexical scope
+ *   LexicalEnvironmentObject[this=global]
  *       |
  *   WithEnvironmentObject wrapping target
  *       |
- *   LexicalEnvironmentObject
+ *   LexicalEnvironmentObject[this=target]
+ *
+ * B.2 Subscript loading (Shared-global JSM)
+ *
+ * The target object of a subscript load may be in a JSM with a shared global,
+ * in which case we will also have the NonSyntacticVariablesObject on the
+ * chain.
  *
- * C. Frame scripts
+ *   Target object's global
+ *       |
+ *   LexicalEnvironmentObject[this=global]
+ *       |
+ *   NonSyntacticVariablesObject
+ *       |
+ *   LexicalEnvironmentObject[this=nsvo]
+ *       |
+ *   WithEnvironmentObject wrapping target
+ *       |
+ *   LexicalEnvironmentObject[this=target]
+ *
+ * D. Frame scripts
  *
  * XUL frame scripts are always loaded with a NonSyntacticVariablesObject as a
  * "polluting global". This is done exclusively in
  * js::ExecuteInGlobalAndReturnScope.
  *
  *   Loader global
  *       |
- *   Global lexical scope
+ *   LexicalEnvironmentObject[this=global]
  *       |
  *   NonSyntacticVariablesObject
  *       |
- *   LexicalEnvironmentObject
+ *   LexicalEnvironmentObject[this=global]
  *
  * D. XBL and DOM event handlers
  *
  * XBL methods are compiled as functions with XUL elements on the env chain,
  * and DOM event handlers are compiled as functions with HTML elements on the
- * env chain. For a chain of elements e0,...,eN:
+ * env chain. For a chain of elements e0,e1,...:
  *
  *      ...
  *       |
- *   WithEnvironmentObject wrapping eN
- *       |
- *      ...
+ *   WithEnvironmentObject wrapping e1
  *       |
  *   WithEnvironmentObject wrapping e0
  *       |
  *   LexicalEnvironmentObject
  *
  */
 
 class EnvironmentObject : public NativeObject