Update Flutter (#495)

diff --git a/Dockerfile b/Dockerfile
index 8730160..a9a1a09 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -6,7 +6,7 @@
 # To retrieve this value, please run the following in your closest shell:
 #
 # $ (cd flutter && git rev-parse HEAD)
-ARG FLUTTER_COMMIT=e6b0f5f238d7c67a686e54d09c91e654fa8f215d
+ARG FLUTTER_COMMIT=58cad787d89cc12e72f1f0ec3f1df6a9796ef029
 
 # We install unzip and remove the apt-index again to keep the
 # docker image diff small.
diff --git a/flutter b/flutter
index e6b0f5f..58cad78 160000
--- a/flutter
+++ b/flutter
@@ -1 +1 @@
-Subproject commit e6b0f5f238d7c67a686e54d09c91e654fa8f215d
+Subproject commit 58cad787d89cc12e72f1f0ec3f1df6a9796ef029
diff --git a/pubspec.lock b/pubspec.lock
index afe3ad5..9529ecd 100644
--- a/pubspec.lock
+++ b/pubspec.lock
@@ -98,7 +98,7 @@
       name: build_runner_core
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "4.5.2"
+    version: "4.5.3"
   built_collection:
     dependency: transitive
     description:
@@ -147,7 +147,7 @@
       name: codemirror
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.5.14+5.52.0"
+    version: "0.5.15+5.52.2"
   collection:
     dependency: transitive
     description:
@@ -308,7 +308,7 @@
       name: http_parser
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "3.1.3"
+    version: "3.1.4"
   http_server:
     dependency: transitive
     description: