"Reverting 41571"

sdk/bin/docgen

Index: sdk/bin/docgen
diff --git a/sdk/bin/docgen b/sdk/bin/docgen
index c6c545542d7900b6c0219ffad6be41bdac4d61dd..bf807ad96d5522187d9e3921bc8d924c60202c8a 100755
--- a/sdk/bin/docgen
+++ b/sdk/bin/docgen
@@ -3,5 +3,34 @@
 # 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.
 
-echo "The 'docgen' name is deprecated. Prefer 'dartdocgen' instead."
-dartdocgen "$@"
+function follow_links() {
+  file="$1"
+  while [ -h "$file" ]; do
+    # On Mac OS, readlink -f doesn't work.
+    file="$(readlink "$file")"
+  done
+  echo "$file"
+}
+
+# Unlike $0, $BASH_SOURCE points to the absolute path of this file.
+PROG_NAME="$(follow_links "$BASH_SOURCE")"
+
+# Handle the case where dart-sdk/bin has been symlinked to.
+BIN_DIR="$(cd "${PROG_NAME%/*}" ; pwd -P)"
+
+SDK_DIR="$(cd "${BIN_DIR}/.." ; pwd -P)"
+
+unset SNAPSHOT
+
+SNAPSHOT="$BIN_DIR/snapshots/utils_wrapper.dart.snapshot"
+
+if test -f "$SNAPSHOT"; then
+  exec "$BIN_DIR"/dart \
+      "--package-root=$BIN_DIR/../packages/" "--old_gen_heap_size=1024" \
+      "$SNAPSHOT" \
+       docgen "--sdk=$SDK_DIR" "$@"
+else
+  exec "$BIN_DIR"/dart \
+      "--package-root=$BIN_DIR/../packages/" "--old_gen_heap_size=1024" \
+      "$BIN_DIR/../../pkg/docgen/bin/docgen.dart" "--sdk=$SDK_DIR" "$@"
+fi