add a debugger UI (#80)

* prototype debugger

* update styles

* update to the latest vm_service_lib

* use the new getScripts() API

* debugger updates

* implement async stepping; separate css

* handle breaking on exceoptions

* remove a todo

* initial debugger tests

* implement tests for debugging functionality

* add a console; display object toString() result

* typo

* allow non-flutter selected isolates

* move the debugger example

* revert back to an older sdk

* review comments

Author: devoncarew

.gitignore

@@ -8,6 +8,7 @@ build/
 pubspec.lock
 
 .idea/
+.data_dir/
 
 # Directory created by dartdoc
 # If you don't generate documentation locally you can remove this line.

analysis_options.yaml

@@ -93,7 +93,6 @@ linter:
     # - parameter_assignments # we do this commonly
     - prefer_adjacent_string_concatenation
     - prefer_asserts_in_initializer_lists
-    - prefer_bool_in_asserts
     - prefer_collection_literals
     - prefer_conditional_assignment
     - prefer_const_constructors

lib/debugger/debugger.css

@@ -0,0 +1,52 @@
+/* Copyright 2019 The Chromium Authors. All rights reserved. */
+/* Use of this source code is governed by a BSD-style license that can be */
+/* found in the LICENSE file. */
+
+.debugger-menu {
+    width: 280px;
+    margin-right: 18px;
+}
+
+.source-head {
+    font-weight: 600;
+    color: #586069;
+    background-color: #f3f3f3;
+    border-bottom: 1px solid #dfe2e5;
+    padding: 4px 8px;
+}
+
+.breakpoints {
+    width: 1em;
+}
+
+.CodeMirror-gutter-elt .octicon {
+    margin-left: 4px;
+    color: #4078c0;
+}
+
+.CodeMirror-linebackground.executionLine {
+    background: #c4daf7;
+}
+
+.execution-marker {
+    color: #4078c0;
+    margin-left: -2px;
+    margin-top: -2px;
+    z-index: 10;
+}
+
+.break-on-exceptions {
+    line-height: 28px;
+}
+
+.break-on-exceptions label {
+    margin-left: 6px;
+}
+
+#resume-button {
+    min-width: 90px
+}
+
+.debugger-items-list {
+    overflow-y: scroll;
+}