Revert "Roll Dart to ac6d4f7e653deba11d4836768376537893a9e9d6. (#6549)" (flutter/engine#6568)

This reverts commit 1743aff91e.

We revert because it breaks the engine to framework roll. Reverting as
soon as possible allows other engine commits to roll into framework
first so we'll have smaller engine rolls which is good for triaging
regressions.

TBR: rmacnak-google

DEPS

@@ -31,7 +31,7 @@ vars = {
   # Dart is: https://github.com/dart-lang/sdk/blob/master/DEPS.
   # You can use //tools/dart/create_updated_flutter_deps.py to produce
   # updated revision list of existing dependencies.
-  'dart_revision': 'ac6d4f7e653deba11d4836768376537893a9e9d6',
+  'dart_revision': 'b99bcfd3099f0d32e39287160a9539e878cb0b68',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py

engine/src/flutter/runtime/BUILD.gn

@@ -6,6 +6,41 @@ import("//third_party/dart/runtime/bin/vmservice/vmservice_sources.gni")
 import("$flutter_root/common/config.gni")
 import("$flutter_root/testing/testing.gni")
 
+action("gen_embedded_resources_cc") {
+  script = "//third_party/dart/runtime/tools/create_resources.py"
+  output_file = "$target_gen_dir/embedded_resources.cc"
+  outputs = [
+    output_file,
+  ]
+
+  inputs = rebase_path(vmservice_sources,
+                       "",
+                       "//third_party/dart/runtime/bin/vmservice")
+
+  args = [
+           "--output",
+           rebase_path(output_file),
+           "--outer_namespace",
+           "flutter",
+           "--inner_namespace",
+           "runtime",
+           "--table_name",
+           "flutter_embedded_service_isolate",
+           "--root_prefix",
+           rebase_path("//third_party/dart/runtime/bin/"),
+         ] + rebase_path(inputs)
+}
+
+source_set("embedded_resources_cc") {
+  sources = [
+    "$target_gen_dir/embedded_resources.cc",
+  ]
+  deps = [
+    ":gen_embedded_resources_cc",
+  ]
+  public_configs = [ "$flutter_root:config" ]
+}
+
 source_set("test_font") {
   sources = [
     "test_font_data.cc",
@@ -49,6 +84,7 @@ source_set("runtime") {
   ]
 
   deps = [
+    ":embedded_resources_cc",
     ":test_font",
     "$flutter_root/assets",
     "$flutter_root/common",