Roll dart sdk to e6d7d67. (flutter#5165)

* Roll dart sdk to e6d7d67.

Changes since last dart roll:

```
e6d7d67 Revert 4f18af1 as it causes test breakages.
4877587 [GN] Uses dart_action.gni instead of compiled_action.gni.
4b89ba2 Meta CHANGELOG markdown cleanup.
3d688de Bump analysis server version to 1.20.2
0dc81ae Publish package:meta 1.1.5
7e54844 [vm] Fix build for gcc 7.3.0.
9d10a6a Issue 33034. Fix statement completion with missing condition right parenthesis.
3fd2d5f [vm] Use compiler warnings to insist callers check for errors from Dart_Invoke*/Load*/Compile*.
afb490a [dart:io] Provide modern Dart-styled constants
2929b71 [kernel/vm] Address follow-up review comments for bytecode generation
73768a5 General TypeInfo and IdentifierContext cleanup
e93b2ee Improve typedef identifier recovery
46a9ed0 Added example about calling a tear-off with a wrong-shape argument list
0c839cf [fasta] Add 'as' expressions to the Forest API
16f6ce2 [release] Prepare changelog for 2.0.0-dev.53.0
d13bf49 Check type-variable bounds on generic methods
794fe1e Add stacktrace tests for synchronous async
fb779df [frontend-server] Disable depfile test on Windows.
```

* Adjust gn-scripts to accommodate 4877587 refactoring.

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': '2765fcf2aecd3841d082fedaeafc00a73a965f8c',
+  'dart_revision': 'e6d7d67f4b35556805dd083fed15bf3ed41f7e33',
 
   'dart_args_tag': '1.4.1',
   'dart_async_tag': '2.0.6',

lib/snapshot/BUILD.gn

@@ -3,6 +3,7 @@
 # found in the LICENSE file.
 
 import("$flutter_root/lib/ui/dart_ui.gni")
+import("//build/compiled_action.gni")
 import("//third_party/dart/utils/compile_platform.gni")
 import("//third_party/dart/utils/generate_entry_points_json.gni")
 
@@ -257,6 +258,53 @@ group("kernel_platform_files") {
   ]
 }
 
+# Template to generate entry points JSON file using gen_snapshot tool.
+# List of entry points is generated as a by-product while doing precompilation.
+#
+# This template expects the following arguments:
+#  - input: Name of the input dart script for precompilation.
+#  - output: Name of the output entry points JSON file.
+#  - extra_args: Extra arguments to pass to dart_bootstrap (optional).
+#  - extra_inputs: Extra input dependencies (optional).
+#
+template("generate_entry_points_json_with_gen_snapshot") {
+  assert(defined(invoker.input), "Must define input dart script")
+  assert(defined(invoker.output), "Must define output json file")
+  extra_args = []
+  if (defined(invoker.extra_args)) {
+    extra_args += invoker.extra_args
+  }
+  extra_inputs = []
+  if (defined(invoker.extra_inputs)) {
+    extra_inputs += invoker.extra_inputs
+  }
+  compiled_action(target_name) {
+    # Printing precompiler entry points is folded into precompilation, so gen_snapshot is invoked
+    # with correct arguments to generate app-aot snapshot.
+
+    input = invoker.input
+    output = invoker.output
+
+    tool = "//third_party/dart/runtime/bin:gen_snapshot"
+    inputs = [
+      input,
+    ] + extra_inputs
+    outputs = [
+      output,
+    ]
+    args = [
+      "--print-precompiler-entry-points=" + rebase_path(output),
+      "--snapshot-kind=app-aot-blobs",
+      "--vm_snapshot_data=" + rebase_path("$target_gen_dir/dummy.vm_data.snapshot"),
+      "--vm_snapshot_instructions=" + rebase_path("$target_gen_dir/dummy.vm_instr.snapshot"),
+      "--isolate_snapshot_data=" + rebase_path("$target_gen_dir/dummy.isolate_data.snapshot"),
+      "--isolate_snapshot_instructions=" + rebase_path("$target_gen_dir/dummy.isolate_instr.snapshot"),
+    ] + extra_args + [
+      rebase_path(input),
+    ]
+  }
+}
+
 generate_entry_points_json_with_gen_snapshot("entry_points_json") {
   input = "$flutter_root/lib/snapshot/snapshot.dart"
   output = "$root_out_dir/dart_entry_points/entry_points.json"

travis/licenses_golden/licenses_third_party

@@ -1,4 +1,4 @@
-Signature: f8b0fa85dcfda661056db3508100fa23
+Signature: 77a39e3d3c589aa9c295c23e102794e6
 
 UNUSED LICENSES: