Elements. Remove PrefixElementImpl.

For now, we have a not nice looking way to write / read Element(s). Most
of the elements are stored as their first fragment, and then asked for
elements. I start with PrefixElementImpl2 to stop doing this, and switch
to writing actual element reference. When we are done with all elements,
it will become nice again.

Change-Id: Ia18c2ab516ae06dc0da0b1ab022f217bf9a7400d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/431702
Reviewed-by: Paul Berry <paulberry@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

https://dart.googlesource.com/sdk/+/676df8b25813bd13a9f9aecd1cb35c66a7e2741f

DEPS

diff --git a/DEPS b/DEPS
index cc51fcf..ae8fba2 100644
--- a/DEPS
+++ b/DEPS
@@ -235,7 +235,7 @@
 ]
 
 deps = {
-  'flutter/engine/src/flutter/third_party/dart': Var('dart_git') + '/sdk' + '@' + 'eba91c5045d612a6cbca7b5ae4e62388a07980e4',
+  'flutter/engine/src/flutter/third_party/dart': Var('dart_git') + '/sdk' + '@' + '676df8b25813bd13a9f9aecd1cb35c66a7e2741f',
 
   'flutter': Var('flutter_git') + '/mirrors/flutter' + '@' + 'e8366e333494ec1b957460657c6d7bda753a167f',
 

commits.json

diff --git a/commits.json b/commits.json
index a32c420..1452b31 100644
--- a/commits.json
+++ b/commits.json
@@ -1,4 +1,4 @@
 {
   "flutter":"e8366e333494ec1b957460657c6d7bda753a167f",
-  "flutter/engine/src/flutter/third_party/dart":"eba91c5045d612a6cbca7b5ae4e62388a07980e4"
+  "flutter/engine/src/flutter/third_party/dart":"676df8b25813bd13a9f9aecd1cb35c66a7e2741f"
 }
\ No newline at end of file