Add _embedder.yaml support to analyzer and analysis_server

pkg/analysis_server/lib/src/context_manager.dart

Index: pkg/analysis_server/lib/src/context_manager.dart
diff --git a/pkg/analysis_server/lib/src/context_manager.dart b/pkg/analysis_server/lib/src/context_manager.dart
index 7c167f942cfcada298fbb2b04d4beb993a9de241..4878ba329845439419898d9b7cc77a73476f1663 100644
--- a/pkg/analysis_server/lib/src/context_manager.dart
+++ b/pkg/analysis_server/lib/src/context_manager.dart
@@ -15,6 +15,7 @@ import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/instrumentation/instrumentation.dart';
 import 'package:analyzer/plugin/options.dart';
 import 'package:analyzer/source/analysis_options_provider.dart';
+import 'package:analyzer/source/embedder.dart';
 import 'package:analyzer/source/package_map_provider.dart';
 import 'package:analyzer/source/package_map_resolver.dart';
 import 'package:analyzer/source/path_filter.dart';
@@ -1409,6 +1410,7 @@ class PackageMapDisposition extends FolderDisposition {
   Iterable<UriResolver> createPackageUriResolvers(
           ResourceProvider resourceProvider) =>
       <UriResolver>[
+        new EmbedderUriResolver(packageMap),

[pquitslund, 2015/11/11 19:19:09]

A consequence of doing the _embedder.yaml discovery in the resolver is that
we'll need to do it again for options.  It might be better if we could do that
just once?  (Aside: there's technically a race condition too in case that file
gets changed between reads but that's a bit pathological.)

What about hoisting that logic up and into context_manager and passing in the
discovered yaml file(s)?

[Brian Wilkerson, 2015/11/11 22:09:14]

What do you mean by "options"?

[pquitslund, 2015/11/11 23:17:16]

Analysis options can also be set by embedders in this file.  They will set the
defaults (available for overriding in a local `.analysis_options` file).

[Brian Wilkerson, 2015/11/11 23:59:36]

Right! I'd forgotten. Thanks.

         new SdkExtUriResolver(packageMap),
         new PackageMapUriResolver(resourceProvider, packageMap)
       ];
@@ -1439,7 +1441,8 @@ class PackagesFileDisposition extends FolderDisposition {
           packageMap[name] = <Folder>[resourceProvider.getFolder(path)];
         }
       });
-      return <UriResolver>[new SdkExtUriResolver(packageMap)];
+      return <UriResolver>[new EmbedderUriResolver(packageMap),
+                           new SdkExtUriResolver(packageMap)];
     } else {
       return const <UriResolver>[];
     }