Merge pull request tc39#19 from EricSL/patch-1

Deprecate x_google_ignoreList in favor of ignoreList, remove Known Extensions

source-map.bs

@@ -146,7 +146,8 @@ following structure:
   "sources": ["foo.js", "bar.js"],
   "sourcesContent": [null, null],
   "names": ["src", "maps", "are", "fun"],
-  "mappings": "A,AAAB;;ABCDE;"
+  "mappings": "A,AAAB;;ABCDE;",
+  "ignoreList": [0]
 }
 ```
 
@@ -180,6 +181,14 @@ can't be hosted.  The contents are listed in the same order as the [=sources=].
 
 <dfn><code>mappings</code></dfn> a string with the encoded mapping data (see [[#mappings-structure]]).
 
+<dfn><code>ignoreList</code></dfn> an optional list of indices of files that
+should be considered third party code, such as framework code or bundler-generated code. This 
+allows developer tools to avoid code that developers likely don't want to see
+or step through, without requiring developers to configure this beforehand.
+It refers to the [=sources=] array and lists the indices of all the known third-party sources
+in the source map. Some browsers may also use the deprecated <code>x_google_ignoreList</code>
+field if <code>ignoreList</code> is not present.
+
 Mappings Structure {#mappings-structure}
 ----------------------------------------
 
@@ -245,19 +254,6 @@ organization providing the extension, such as `x_google_linecount`.    Field nam
 the `x_` namespace are reserved for future revisions.  It is recommended that fields be
 namespaced by domain, i.e. `x_com_google_gwt_linecount`.
 
-Known Extensions
-----------------
-
-<dfn export><code>x_google_linecount</code></dfn> The number of lines represented by this source map. 
-
-<dfn export><code>x_google_ignoreList</code></dfn> Identifies third-party sources (such as framework
-code or bundler-generated code), allowing developers to avoid code that they don't want to see
-or step through, without having to configure this beforehand.
-
-It refers to the [=sources=] array and lists the indices of all the known third-party sources
-in that source map.  When parsing the source map, developer tools can use this to determine
-sections of the code that the browser loads and runs that could be automatically ignore-listed.
-
 Notes on File Offsets
 ---------------------