Cherry-picks of multiple html CLs

pkg/dev_compiler/lib/src/compiler/code_generator.dart

Index: pkg/dev_compiler/lib/src/compiler/code_generator.dart
diff --git a/pkg/dev_compiler/lib/src/compiler/code_generator.dart b/pkg/dev_compiler/lib/src/compiler/code_generator.dart
index 7df66d29e2a33d9149355743fefa73b20995cab9..5a5ab9d218155293629629bcb9915d4376921318 100644
--- a/pkg/dev_compiler/lib/src/compiler/code_generator.dart
+++ b/pkg/dev_compiler/lib/src/compiler/code_generator.dart
@@ -6033,8 +6033,7 @@ String jsLibraryName(String libraryRoot, LibraryElement library) {
     // E.g., "foo/bar.dart" and "foo$47bar.dart" would collide.
     qualifiedPath = uri.pathSegments.skip(1).join(encodedSeparator);
   } else if (isWithin(libraryRoot, uri.toFilePath())) {
-    qualifiedPath = uri.path
-        .substring(libraryRoot.length)
+    qualifiedPath = relative(uri.toFilePath(), from: libraryRoot)
         .replaceAll(separator, encodedSeparator);
   } else {
     // We don't have a unique name.
@@ -6059,30 +6058,6 @@ String jsLibraryDebuggerName(String libraryRoot, LibraryElement library) {
   return relative(filePath, from: libraryRoot);
 }
 
-String jsDebuggingLibraryName(String libraryRoot, LibraryElement library) {
-  var uri = library.source.uri;
-  if (uri.scheme == 'dart') {
-    return uri.path;
-  }
-  // TODO(vsm): This is not necessarily unique if '__' appears in a file name.
-  var separator = '__';
-  String qualifiedPath;
-  if (uri.scheme == 'package') {
-    // Strip the package name.
-    // TODO(vsm): This is not unique if an escaped '/'appears in a filename.
-    // E.g., "foo/bar.dart" and "foo$47bar.dart" would collide.
-    qualifiedPath = uri.pathSegments.skip(1).join(separator);
-  } else if (uri.toFilePath().startsWith(libraryRoot)) {
-    qualifiedPath =
-        uri.path.substring(libraryRoot.length).replaceAll('/', separator);
-  } else {
-    // We don't have a unique name.
-    throw 'Invalid library root. $libraryRoot does not contain ${uri
-        .toFilePath()}';
-  }
-  return pathToJSIdentifier(qualifiedPath);
-}
-
 /// Shorthand for identifier-like property names.
 /// For now, we emit them as strings and the printer restores them to
 /// identifiers if it can.