Expand the JSON reporter to enable a progress bar.

json_reporter.md

 JSON Reporter Protocol
 ======================
 
 The test runner supports a JSON reporter which provides a machine-readable
 representation of the test runner's progress. This reporter is intended for use
 by IDEs and other tools to present a custom view of the test runner's operation
 without needing to parse output intended for humans.
 
 Note that the test runner is highly asynchronous, and users of this protocol
 shouldn't make assumptions about the ordering of events beyond what's explicitly
@@ skipping 83 matching lines @@
   String protocolVersion;
 
   // The version of the test runner being used.
   String runnerVersion;
 }
 ```
 
 A single start event is emitted before any other events. It indicates that the
 test runner has started running.
 
+### SuiteCountEvent

[alexander.doroshko, 2016/01/29 11:51:05]

mismatch with the class name AllSuitesEvent

+
+```
+class AllSuitesEvent {
+  String type = "allSuites";
+
+  /// The total number of suites that will be loaded.
+  int count;
+}
+```
+
+A single suite count event is emitted once the test runner knows the total
+number of suites that will be loaded over the course of the test run. Because
+this is determined asynchronously, its position relative to other events (except
+`StartEvent`) is not guaranteed.
+
 ### SuiteEvent
 
 ```
 class SuiteEvent extends Event {
   String type = "suite";
 
   /// Metadata about the suite.
   Suite suite;
 }
 ```
@@ skipping 208 matching lines @@
   String? name;
 
   // The ID of the suite containing this group.
   int suiteID;
 
   // The ID of the group's parent group, unless it's the root group.
   int? parentID;
 
   // The group's metadata, including metadata from any containing groups.
   Metadata metadata;
+
+  // The number of tests (recursively) within this group.
+  int testCount;
 }
 ```
 
 A group containing test cases. The group's ID is unique in the context of this
 test run. It's used elsewhere in the protocol to refer to this group without
 including its full representation.
 
 The implicit group at the root of each test suite has `null` `name` and
 `parentID` attributes.
 
 ### Metadata
 
 ```
 class Metadata {
   // Whether the test case will be skipped by the test runner.
   bool skip;
 
   // The reason the test case is skipped, if the user provided it.
   String? skipReason;
 }
 ```
 
 The metadata attached to a test by a user.