Start logger in startProgress to avoid assertion failure (#20814)

* Start logger in startProgress to avoid assertion failure

There are lots of places that create a Status() and all but two of them call ..start() immediately. This is one of the places that doesn't, which causes an assertion failure when running with --enable-asserts and the other is in the same file (I suspect it's also incorrect, but possibly it's never used - I'll look at that separately when I can trace some code that calls it).

Fixes #20812.

* Enable asserts for tools tests

* Fix lint

* Rename enableAsserts -> enableFlutterToolAsserts

To make it clearer that it only enables asserts for flutter_tools when set.

dev/bots/test.dart

@@ -294,7 +294,10 @@ Future<Null> _runSmokeTests() async {
 Future<Null> _runToolTests() async {
   await _runSmokeTests();
 
-  await _pubRunTest(path.join(flutterRoot, 'packages', 'flutter_tools'));
+  await _pubRunTest(
+    path.join(flutterRoot, 'packages', 'flutter_tools'),
+    enableFlutterToolAsserts: true,
+  );
 
   print('${bold}DONE: All tests successful.$reset');
 }
@@ -346,6 +349,7 @@ Future<Null> _runCoverage() async {
 Future<Null> _pubRunTest(
   String workingDirectory, {
   String testPath,
+  bool enableFlutterToolAsserts = false
 }) {
   final List<String> args = <String>['run', 'test', '-j1', '-rcompact'];
   if (!hasColor)
@@ -356,6 +360,14 @@ Future<Null> _pubRunTest(
   if (new Directory(pubCache).existsSync()) {
     pubEnvironment['PUB_CACHE'] = pubCache;
   }
+  if (enableFlutterToolAsserts) {
+    // If an existing env variable exists append to it, but only if
+    // it doesn't appear to already include enable-asserts.
+    String toolsArgs = Platform.environment['FLUTTER_TOOL_ARGS'] ?? '';
+    if (!toolsArgs.contains('--enable-asserts'))
+        toolsArgs += ' --enable-asserts';
+    pubEnvironment['FLUTTER_TOOL_ARGS'] = toolsArgs.trim();
+  }
   return _runCommand(
     pub, args,
     workingDirectory: workingDirectory,

packages/flutter_tools/lib/src/commands/daemon.dart

@@ -908,7 +908,7 @@ class _AppRunLogger extends Logger {
         'progressId': progressId,
         'finished': true
       });
-    });
+    })..start();
     return _status;
   }