Consolidate observatory code (#3892)

* rename service_protocol.dart to protocol_discovery.dart

* add a wrapper around the obs. protocol

* use json-rpc in run

* consolidate obs. code; implement flutter run --benchmark

* review comments

packages/flutter_tools/lib/src/ios/simulators.dart

diff --git a/packages/flutter_tools/lib/src/ios/simulators.dart b/packages/flutter_tools/lib/src/ios/simulators.dart
index 2494cc9..02e47b1 100644
--- a/packages/flutter_tools/lib/src/ios/simulators.dart
+++ b/packages/flutter_tools/lib/src/ios/simulators.dart
@@ -15,7 +15,7 @@
 import '../device.dart';
 import '../flx.dart' as flx;
 import '../globals.dart';
-import '../service_protocol.dart';
+import '../protocol_discovery.dart';
 import 'mac.dart';
 
 const String _xcrunPath = '/usr/bin/xcrun';
@@ -395,20 +395,17 @@
     RegExp versionExp = new RegExp(r'iPhone ([0-9])+');
     Match match = versionExp.firstMatch(name);
 
-    if (match == null) {
-      // Not an iPhone. All available non-iPhone simulators are compatible.
+    // Not an iPhone. All available non-iPhone simulators are compatible.
+    if (match == null)
       return true;
-    }
 
-    if (int.parse(match.group(1)) > 5) {
-      // iPhones 6 and above are always fine.
+    // iPhones 6 and above are always fine.
+    if (int.parse(match.group(1)) > 5)
       return true;
-    }
 
     // The 's' subtype of 5 is compatible.
-    if (name.contains('iPhone 5s')) {
+    if (name.contains('iPhone 5s'))
       return true;
-    }
 
     _supportMessage = "The simulator version is too old. Choose an iPhone 5s or above.";
     return false;
@@ -447,12 +444,10 @@
     if (!(await _setupUpdatedApplicationBundle(app)))
       return new LaunchResult.failed();
 
-    ServiceProtocolDiscovery observatoryDiscovery;
+    ProtocolDiscovery observatoryDiscovery;
 
-    if (debuggingOptions.debuggingEnabled) {
-      observatoryDiscovery = new ServiceProtocolDiscovery(
-        logReader, ServiceProtocolDiscovery.kObservatoryService);
-    }
+    if (debuggingOptions.debuggingEnabled)
+      observatoryDiscovery = new ProtocolDiscovery(logReader, ProtocolDiscovery.kObservatoryService);
 
     // Prepare launch arguments.
     List<String> args = <String>[