Roll dart and buildroot deps. (#3842)

* Roll dart and buildroot deps since they have to be updated together to get and use prebuilt dart sdk in correct location.

* Update license

DEPS

@@ -30,7 +30,7 @@ vars = {
   # Dart is: https://github.com/dart-lang/sdk/blob/master/DEPS.
   # You can use //dart/tools/create_updated_fluter_deps.py to produce
   # updated revision list of existing dependencies.
-  'dart_revision': '3c543bb210711dd6761d592a863fd6f32e1f1279',
+  'dart_revision': '501688de4cb6ba62a5bfe655361edf122cc1d7fc',
 
   'dart_args_tag': '0.13.7',
   'dart_async_tag': 'daf66909019d2aaec1721fc39d94ea648a9fdc1d',
@@ -75,7 +75,7 @@ allowed_hosts = [
 ]
 
 deps = {
-  'src': 'https://github.com/flutter/buildroot.git' + '@' + '10383548a4063ad75855527a745e324125cf2210',
+  'src': 'https://github.com/flutter/buildroot.git' + '@' + '214524470c62170604261d1bed7270015c54a9b4',
 
    # Fuchsia compatibility
    #

travis/licenses_golden/licenses_dart

-Signature: e340d89dea11ef56c6e266495ffa53b0
+Signature: 6cb33f49531d29e621f7ab4b0aa6bac1
 
 UNUSED LICENSES:
 
@@ -1051,6 +1051,7 @@ FILE: ../../../dart/runtime/observatory/lib/src/elements/class_tree.dart
 FILE: ../../../dart/runtime/observatory/lib/src/elements/debugger.dart
 FILE: ../../../dart/runtime/observatory/lib/src/elements/heap_map.dart
 FILE: ../../../dart/runtime/observatory/lib/src/elements/isolate_reconnect.dart
+FILE: ../../../dart/runtime/observatory/lib/src/elements/memory_dashboard.dart
 FILE: ../../../dart/runtime/observatory/lib/src/elements/metrics.dart
 FILE: ../../../dart/runtime/observatory/lib/src/elements/vm_connect.dart
 FILE: ../../../dart/runtime/observatory/lib/src/service/object.dart
@@ -1381,6 +1382,7 @@ FILE: ../../../dart/runtime/observatory/lib/src/models/repositories/allocation_p
 FILE: ../../../dart/runtime/observatory/lib/src/models/repositories/breakpoint.dart
 FILE: ../../../dart/runtime/observatory/lib/src/models/repositories/class.dart
 FILE: ../../../dart/runtime/observatory/lib/src/models/repositories/context.dart
+FILE: ../../../dart/runtime/observatory/lib/src/models/repositories/editor.dart
 FILE: ../../../dart/runtime/observatory/lib/src/models/repositories/eval.dart
 FILE: ../../../dart/runtime/observatory/lib/src/models/repositories/event.dart
 FILE: ../../../dart/runtime/observatory/lib/src/models/repositories/field.dart
@@ -1413,6 +1415,7 @@ FILE: ../../../dart/runtime/observatory/lib/src/repositories/allocation_profile.
 FILE: ../../../dart/runtime/observatory/lib/src/repositories/breakpoint.dart
 FILE: ../../../dart/runtime/observatory/lib/src/repositories/class.dart
 FILE: ../../../dart/runtime/observatory/lib/src/repositories/context.dart
+FILE: ../../../dart/runtime/observatory/lib/src/repositories/editor.dart
 FILE: ../../../dart/runtime/observatory/lib/src/repositories/eval.dart
 FILE: ../../../dart/runtime/observatory/lib/src/repositories/event.dart
 FILE: ../../../dart/runtime/observatory/lib/src/repositories/field.dart