[dart2js] Cache deferred JS AST bodies during printing and source map generation.

There was a bug in source map generation introduced by this deferring. A map from JS Nodes to source map info is being shared between these two operations and in order to look up nodes in the map, the Node objects must be the same.

This gives up some but not all of the gains from deferring these function bodies. I'm working on a more long term fix that combines these two passes of the AST.

Bugs: https://github.com/dart-lang/sdk/issues/53466
Change-Id: If25d1b24dd32456155e8802725d480454c71d2b6
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/325600
Reviewed-by: Stephen Adams <sra@google.com>
Commit-Queue: Nate Biggs <natebiggs@google.com>

https://dart.googlesource.com/sdk/+/655687db777cf07cb4d75398f9eaf2d30ab6af44

DEPS

diff --git a/DEPS b/DEPS
index 3d92e4e..1c4847a 100644
--- a/DEPS
+++ b/DEPS
@@ -266,7 +266,7 @@
 
   'engine/src/flutter': Var('flutter_git') + '/mirrors/engine' + '@' + '7c78ea210c194ebaba08189ae116fe021b48d716',
 
-  'engine/src/third_party/dart': Var('dart_git') + '/sdk' + '@' + 'b35c6453025fd3d497441f49cd2252fde4389b5e',
+  'engine/src/third_party/dart': Var('dart_git') + '/sdk' + '@' + '655687db777cf07cb4d75398f9eaf2d30ab6af44',
 
   'flutter': Var('flutter_git') + '/mirrors/flutter' + '@' + '6c7ddb859dc56e4f01fe7bd9f318689db3f5ee2e',
 

commits.json

diff --git a/commits.json b/commits.json
index b975537..f92c39f 100644
--- a/commits.json
+++ b/commits.json
@@ -1,5 +1,5 @@
 {
   "engine/src/flutter":"7c78ea210c194ebaba08189ae116fe021b48d716",
-  "engine/src/third_party/dart":"b35c6453025fd3d497441f49cd2252fde4389b5e",
+  "engine/src/third_party/dart":"655687db777cf07cb4d75398f9eaf2d30ab6af44",
   "flutter":"6c7ddb859dc56e4f01fe7bd9f318689db3f5ee2e"
 }
\ No newline at end of file