Make sure that a Dialog doesn't crash in 0x0 environment (#174023)

This is my attempt to handle
https://github.com/flutter/flutter/issues/6537 for the Dialog UI
control.

Co-authored-by: Tong Mu <dkwingsmt@users.noreply.github.com>
https://dart.googlesource.com/external/github.com/flutter/flutter/+/0fe60b15a2664e4f03f64459c32ff970a51eb054

DEPS

diff --git a/DEPS b/DEPS
index b529904..86dc3ce 100644
--- a/DEPS
+++ b/DEPS
@@ -231,7 +231,7 @@
 deps = {
   'flutter/engine/src/flutter/third_party/dart': Var('dart_git') + '/sdk' + '@' + '3f120e0e9e6271b7b8fe5a2b8e1199e3e35c1329',
 
-  'flutter': Var('flutter_git') + '/mirrors/flutter' + '@' + '05fbe0ed1bbc1bd9478a526a5ca254f967a3b2b7',
+  'flutter': Var('flutter_git') + '/mirrors/flutter' + '@' + '0fe60b15a2664e4f03f64459c32ff970a51eb054',
 
   'flutter/engine/src/flutter/third_party/depot_tools':
   Var('chromium_git') + '/chromium/tools/depot_tools.git' + '@' + '580b4ff3f5cd0dcaa2eacda28cefe0f45320e8f7',

commits.json

diff --git a/commits.json b/commits.json
index 0de7ba8..450aa3f 100644
--- a/commits.json
+++ b/commits.json
@@ -1,4 +1,4 @@
 {
-  "flutter":"05fbe0ed1bbc1bd9478a526a5ca254f967a3b2b7",
+  "flutter":"0fe60b15a2664e4f03f64459c32ff970a51eb054",
   "flutter/engine/src/flutter/third_party/dart":"3f120e0e9e6271b7b8fe5a2b8e1199e3e35c1329"
 }
\ No newline at end of file