Modify apidoc to prefer handwritten HTML5 docs over those in MDN or generated code.

lib/dartdoc/dartdoc.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * To generate docs for a library, run this script with the path to an
  * entrypoint .dart file, like:
  *
  *     $ dart dartdoc.dart foo.dart
  *
@@ skipping 618 matching lines @@
     _totalLibraries++;
     _currentLibrary = library;
     _currentType = null;
 
     startFile(libraryUrl(library));
     writeHeader('${library.name} Library',
         [library.name, libraryUrl(library)]);
     writeln('<h2><strong>${library.name}</strong> library</h2>');
 
     // Look for a comment for the entire library.
-    final comment = _comments.findLibrary(library.baseSource);
+    final comment = getLibraryComment(library);
     if (comment != null) {
-      final html = md.markdownToHtml(comment);
-      writeln('<div class="doc">$html</div>');
+      writeln('<div class="doc">$comment</div>');
     }
 
     // Document the top-level members.
     docMembers(library.topType);
 
     // Document the types.
     final classes = <Type>[];
     final interfaces = <Type>[];
     final exceptions = <Type>[];
 
@@ skipping 393 matching lines @@
 
     if (includeSource && showCode) {
       writeln('<pre class="source">');
       writeln(md.escapeHtml(unindentCode(span)));
       writeln('</pre>');
     }
 
     writeln('</div>');
   }
 
+
+  /** Get the doc comment associated with the given library. */
+  String getLibraryComment(Library library) {
+    // Look for a comment for the entire library.
+    final comment = _comments.findLibrary(library.baseSource);
+    if (comment != null) {
+      return md.markdownToHtml(comment);
+    }
+    return null;
+  }
+
   /** Get the doc comment associated with the given type. */
   String getTypeComment(Type type) {
     String comment = _comments.find(type.span);
     if (comment == null) return null;
     return commentToHtml(comment);
   }
 
   /** Get the doc comment associated with the given method. */
   String getMethodComment(MethodMember method) {
     String comment = _comments.find(method.span);
@@ skipping 311 matching lines @@
       if (filename.endsWith('appcache.manifest')) {
         return;
       }
       var relativePath = filename.substring(pathPrefixLength + 1);
       write("$relativePath\n");
     };
     toCache.onDone = (done) => endFile();
     toCache.list(recursive: true);
   }
 }