Roll dart. (flutter#4902)

* Roll dart.

Changes since last roll:

4da5228 [frontend-server] Return non-zero exit code if there are errors.
d7a540b Document --enable-asserts in dart2js's help, and remove --checked.
d9c3190 [vm] Remove some bin -> vm includes.
3dcdaf9 [vm] Check for OOM when allocating a new handle block.
865f527 [dart:io] Adds IOOverrides.socketConnect
f858e5d Replace Token.previous usage in BodyBuilder
f66532b Replace more occurrences of token.previous with findPrevious
d46915d Bring in the latest pub
7470f41 Clean up documentation of command-line analyzer options
4b68234 [ VM / Dart 2 ] Marked tests that exercise functionality not supported in Dart 2 as SkipByDesign.
859632b Fixes for uninitialized fields of Flutter widgets create constructors in Flutter style.
c9e9c1d Remove dart:isolate runtime support in DDC
0482cf4 [fuchsia] Add rules to build gen_snapshot targeting Fuchsia
2de8241 Make isolate patch play nice with web workers.
be3baa0 Additional ExprBuilder implementation.
42581e4 [VM] Added '--enable-asserts' to the top-level help message.
44dbba2 Use offset/length of the import prefix, or empty. Same for constructor names.
85b4c60 [VM runtime] Improve type error messages in Dart 2 (fixes flutter#32564). Hide private class _Future and map it to core lib class Future. In Dart 2, show dynamic as type argument(s) of raw generic types.
ebdee7e More prep work to allow the linker to re-use resolution logic.
91e6c8b Fix missing_return warning in expr_builder.dart
59de971 Complete Flutter's setState() as a whole statement, with a closure, and the caret inside the closure.
b82e5b4 Replace code completion usage of token.previous with findPrevious
0e8457c Fix for building sequence of identifiers and several tests.
6a84638 Updated for proper failure.
577b168 Fix jsinterop bug: we incorrectly added null values for js-interop constructor calls.
8e02ff9 Added @category annotation for Web libraries and removed createCustomUpgrader.
c60199c [vm/kernel/aot] Tree shaking based on results of TFA, take 2.
b217e21 Mark a few more co19 failures to fix.
70f4553 [kernel] Add field for instantiate-to-bounds algorithm in TypeParameter.
bc75856 Update getClientRects, removed xtab, removed bogus entry in dom.json, expose ServiceWorker, removed query and queryAll from in dart:html, added constructor to MessageChannel and removed getCssCanvasContext.
f9e12f1 step 3 of ??: ignore old options from old FE
c0fa4e2 step 2 of ??: remove unnecessary pattern in -m option
51867f2 step 1 of ??: cleaning up options...

* Update license hash. No license changes.

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': 'e3051175192c83fafa3636c0f16d804734bb285a',
+  'dart_revision': '4da52281aa35b6c1951b3e269a6934412b15b105',
 
   'dart_args_tag': '1.4.1',
   'dart_async_tag': '2.0.6',
@@ -48,7 +48,7 @@ vars = {
   'dart_csslib_tag': '0.14.1',
   'dart_dart2js_info_tag': '0.5.5+1',
   'dart_dart_style_tag': '1.0.10',
-  'dart_dartdoc_tag': 'v0.17.1+1',
+  'dart_dartdoc_tag': 'v0.18.0',
   'dart_fixnum_tag': '0.10.5',
   'dart_glob_tag': '1.1.5',
   'dart_html_tag': '0.13.3',
@@ -75,7 +75,7 @@ vars = {
   'dart_plugin_tag': '0.2.0+2',
   'dart_pool_tag': '1.3.4',
   'dart_protobuf_tag': '0.7.1',
-  'dart_pub_rev': '875d35005a7d33f367d70a3e31e9d3bad5d1ebd8',
+  'dart_pub_rev': 'bc2b5ff80e50b4b1c317230e8963c1fada3cfe73',
   'dart_pub_semver_tag': '1.3.2',
   'dart_quiver_tag': '5aaa3f58c48608af5b027444d561270b53f15dbf',
   'dart_resource_rev': 'af5a5bf65511943398146cf146e466e5f0b95cb9',

travis/licenses_golden/licenses_third_party

@@ -1,4 +1,4 @@
-Signature: 5591b9dbad944ddf64a6bf58db4c153f
+Signature: 240f392a30cdf33f0ddff5fc2cf9241b
 
 UNUSED LICENSES: