Delay the window until the first frame is received from the Flutter engine (#54703)

Fixes https://github.com/flutter/flutter/issues/151098

https://dart.googlesource.com/external/github.com/flutter/engine/+/a02799141d7501318f205a0eb1cffe5c7e1c7193
diff --git a/DEPS b/DEPS
index 093c0aa..01851a7 100644
--- a/DEPS
+++ b/DEPS
@@ -281,7 +281,7 @@
 deps = {
   'engine/src': 'https://github.com/flutter/buildroot.git' + '@' + 'f85c3be4bf808add6ba867b8ff7943fd235b7b5e',
 
-  'engine/src/flutter': Var('flutter_git') + '/mirrors/engine' + '@' + '04bc90bff86cc881d7749007fa8ac3340fed6da6',
+  'engine/src/flutter': Var('flutter_git') + '/mirrors/engine' + '@' + 'a02799141d7501318f205a0eb1cffe5c7e1c7193',
 
   'engine/src/flutter/third_party/dart': Var('dart_git') + '/sdk' + '@' + 'a6a2c57d689c5aca7d9fadd5dbf04615246ed198',
 
diff --git a/commits.json b/commits.json
index 32bbec0..867eddd 100644
--- a/commits.json
+++ b/commits.json
@@ -1,5 +1,5 @@
 {
-  "engine/src/flutter":"04bc90bff86cc881d7749007fa8ac3340fed6da6",
+  "engine/src/flutter":"a02799141d7501318f205a0eb1cffe5c7e1c7193",
   "engine/src/flutter/third_party/dart":"a6a2c57d689c5aca7d9fadd5dbf04615246ed198",
   "flutter":"af21d9f5b360dee1343386bcc02f6ff5bd6d48fa"
 }
\ No newline at end of file