Fixed some bugs in dom docs and recovered documentation of Canvas stuff.

tools/dom/docs/lib/docs.dart

 /**
  * A library for extracting the documentation from the various HTML libraries
  * ([dart:html], [dart:svg], [dart:web_audio], [dart:indexed_db]) and saving
  * those documentation comments to a JSON file.
  */
 
 library docs;
 
 import '../../../../sdk/lib/_internal/compiler/implementation/mirrors/mirrors.dart';
 import '../../../../sdk/lib/_internal/dartdoc/lib/src/json_serializer.dart';
@@ skipping 67 matching lines @@
           (e) => HTML_LIBRARY_NAMES.indexOf(e.uri.toString()) >= 0))
       ..sort((x, y) =>
         x.uri.toString().toUpperCase().compareTo(
         y.uri.toString().toUpperCase()));
 
   for (LibraryMirror libMirror in sortedLibraries) {
     print('Extracting documentation from ${libMirror.displayName}.');
 
     var libraryJson = {};
     var sortedClasses = _sortAndFilterMirrors(
-        libMirror.classes.values.toList());
+        libMirror.classes.values.toList(), ignoreDocsEditable: true);
 
     for (ClassMirror classMirror in sortedClasses) {
       var classJson = {};
       var sortedMembers = _sortAndFilterMirrors(
           classMirror.members.values.toList());
 
       var membersJson = {};
       for (var memberMirror in sortedMembers) {
         var memberDomName = domNames(memberMirror)[0];
         var memberComment = computeUntrimmedCommentAsList(memberMirror);
 
         // Remove interface name from Dom Name.
         if (memberDomName.indexOf('.') >= 0) {
           memberDomName = memberDomName.slice(memberDomName.indexOf('.') + 1);
         }
 
         if (!memberComment.isEmpty) {
           membersJson.putIfAbsent(memberDomName, () => memberComment);
         }
       }
 
+      // Only include the comment if DocsEditable is set.
       var classComment = computeUntrimmedCommentAsList(classMirror);
-      if (!classComment.isEmpty) {
+      if (!classComment.isEmpty &&
+          findMetadata(classMirror.metadata, 'DocsEditable') != null) {
         classJson.putIfAbsent('comment', () => classComment);
       }
       if (!membersJson.isEmpty) {
         classJson.putIfAbsent('members', () =>
             membersJson);
       }
 
       if (!classJson.isEmpty) {
         libraryJson.putIfAbsent(domNames(classMirror)[0], () =>
             classJson);
       }
     }
 
     if (!libraryJson.isEmpty) {
       convertedJson.putIfAbsent(libMirror.displayName, () =>
           libraryJson);
     }
   }
 
   return convertedJson;
 }
 
-List<DeclarationMirror> _sortAndFilterMirrors(List<DeclarationMirror> mirrors) {
-  // Filter out mirrors that are private, or which are not part of this docs
-  // process. That is, ones without the DocsEditable annotation.
+/// Filter out mirrors that are private, or which are not part of this docs
+/// process. That is, ones without the DocsEditable annotation.
+/// If [ignoreDocsEditable] is true, relax the restriction on @DocsEditable.
+/// This is to account for classes that are defined in a template, but whose
+/// members are generated.
+List<DeclarationMirror> _sortAndFilterMirrors(List<DeclarationMirror> mirrors,
+    {ignoreDocsEditable: false}) {
+
   var filteredMirrors = mirrors.where((DeclarationMirror c) =>
       !domNames(c).isEmpty &&
       !c.displayName.startsWith('_') &&
-      (findMetadata(c.metadata, 'DocsEditable') != null))
+      (!ignoreDocsEditable ? (findMetadata(c.metadata, 'DocsEditable') != null)
+          : true))
       .toList();
 
   filteredMirrors.sort((x, y) =>
     domNames(x)[0].toUpperCase().compareTo(
     domNames(y)[0].toUpperCase()));
 
   return filteredMirrors;
 }
 
 /// Given the class mirror, returns the names found or an empty list.
 List<String> domNames(DeclarationMirror mirror) {
   var domNameMetadata = findMetadata(mirror.metadata, 'DomName');
 
   if (domNameMetadata != null) {
     var domNames = <String>[];
     var tags = deprecatedFutureValue(domNameMetadata.getField('name'));
     for (var s in tags.reflectee.split(',')) {
       domNames.add(s.trim());
     }
 
     if (domNames.length == 1 && domNames[0] == 'none') return <String>[];
     return domNames;
   } else {
     return <String>[];
   }
 }