--- a/flutter/tools/gn
+++ b/flutter/tools/gn
@@ -347,17 +347,41 @@
 
 
 def setup_git_versions():
-  revision_args = {}
-
-  engine_path = os.path.join(SRC_ROOT, 'flutter')
-  revision_args['engine_version'] = get_repository_version(engine_path)
-  revision_args['content_hash'] = get_content_hash()
-  skia_path = os.path.join(SRC_ROOT, 'flutter', 'third_party', 'skia')
-  revision_args['skia_version'] = get_repository_version(skia_path)
-
-  revision_args['dart_version'] = get_repository_version(get_dart_path())
-
-  return revision_args
+  engine_ver = os.environ.get("FLUTTER_ENGINE_VERSION")
+  if not engine_ver:
+    try:
+      engine_ver = get_repository_version(os.path.join(SRC_ROOT, 'flutter'))
+    except Exception:
+      engine_ver = "a804b261645ef8c13eb3d5c44a5c2fb0340c5539"
+
+  content_hash = os.environ.get("FLUTTER_CONTENT_HASH")
+  if not content_hash:
+    try:
+      content_hash = get_content_hash()
+    except Exception:
+      content_hash = engine_ver
+
+  skia_ver = os.environ.get("SKIA_VERSION")
+  if not skia_ver:
+    try:
+      skia_path = os.path.join(SRC_ROOT, 'flutter', 'third_party', 'skia')
+      skia_ver = get_repository_version(skia_path)
+    except Exception:
+      skia_ver = "8df24be66531469e576a806749a0202ae26b8d08"
+
+  dart_ver = os.environ.get("DART_VERSION")
+  if not dart_ver:
+    try:
+      dart_ver = get_repository_version(get_dart_path())
+    except Exception:
+      dart_ver = "60a57cd42d64dc03e9f07aa60a2e250755c1ef28"
+
+  return {
+    'engine_version': engine_ver,
+    'content_hash': content_hash,
+    'skia_version': skia_ver,
+    'dart_version': dart_ver,
+  }
 
 
 # pylint: disable=line-too-long