Upgrade dartdoc to 0.15.0+1 (#13432)

* Update dartdoc to 0.15.0+1 for Flutter.

* Minimize change

dev/bots/docs.sh

@@ -19,7 +19,7 @@ if [ -d "$FLUTTER_PUB_CACHE" ]; then
 fi
 
 # Install dartdoc.
-bin/cache/dart-sdk/bin/pub global activate dartdoc 0.14.1
+bin/cache/dart-sdk/bin/pub global activate dartdoc 0.15.0+1
 
 # This script generates a unified doc set, and creates
 # a custom index.html, placing everything into dev/docs/doc.

dev/tools/dartdoc.dart

@@ -109,7 +109,10 @@ dependencies:
     '--header', 'analytics.html',
     '--header', 'survey.html',
     '--footer-text', 'lib/footer.html',
-    '--exclude', 'temp_doc',
+    '--exclude-packages',
+'analyzer,args,barback,cli_util,csslib,front_end,glob,html,http_multi_server,io,isolate,js,kernel,logging,mime,mockito,node_preamble,plugin,shelf,shelf_packages_handler,shelf_static,shelf_web_socket,utf,watcher,yaml',
+    '--exclude',
+  'package:Flutter/temp_doc.dart,package:http/browser_client.dart,package:intl/intl_browser.dart,package:matcher/mirror_matchers.dart,package:quiver/mirrors.dart,pacakge:quiver/io.dart,package:vm_service_client/vm_service_client.dart,package:web_socket_channel/html.dart',
     '--favicon=favicon.ico',
     '--use-categories',
     '--category-order', 'flutter,Dart Core,flutter_test,flutter_driver',