[Impeller] add emulated advanced blend support for exp canvas. (#54020)

Refactors flip backdrop into a shared method and adds supported for emulated advanced blends in exp canvas. Last missing feature (AFAIK).
https://dart.googlesource.com/external/github.com/flutter/engine/+/b1cbf54899fbd21f4eb79beca7a492e32e6fcc96

DEPS

diff --git a/DEPS b/DEPS
index 6f62515..3561957 100644
--- a/DEPS
+++ b/DEPS
@@ -280,7 +280,7 @@
 deps = {
   'engine/src': 'https://github.com/flutter/buildroot.git' + '@' + '327906297b49980748ea1956019829e7c434a03e',
 
-  'engine/src/flutter': Var('flutter_git') + '/mirrors/engine' + '@' + 'fef21a6145cfae6c7b3ea0139eb5c4e0aaee9c52',
+  'engine/src/flutter': Var('flutter_git') + '/mirrors/engine' + '@' + 'b1cbf54899fbd21f4eb79beca7a492e32e6fcc96',
 
   'engine/src/flutter/third_party/dart': Var('dart_git') + '/sdk' + '@' + 'a80097b863c6e649d94b1808952c652d46e39550',
 

commits.json

diff --git a/commits.json b/commits.json
index d377ff3..5c374c3 100644
--- a/commits.json
+++ b/commits.json
@@ -1,5 +1,5 @@
 {
-  "engine/src/flutter":"fef21a6145cfae6c7b3ea0139eb5c4e0aaee9c52",
+  "engine/src/flutter":"b1cbf54899fbd21f4eb79beca7a492e32e6fcc96",
   "engine/src/flutter/third_party/dart":"a80097b863c6e649d94b1808952c652d46e39550",
   "flutter":"660694cb1765d82f00aad45b75e819901207b1d3"
 }
\ No newline at end of file