Initial isolate reload support

runtime/observatory/lib/src/elements/debugger.dart

Index: runtime/observatory/lib/src/elements/debugger.dart
diff --git a/runtime/observatory/lib/src/elements/debugger.dart b/runtime/observatory/lib/src/elements/debugger.dart
index 81541ef595d7032a7b5e2d3f36859e6fee758bc9..61a8989d60b4dd1737a817f739e05a2b6f5fc4c5 100644
--- a/runtime/observatory/lib/src/elements/debugger.dart
+++ b/runtime/observatory/lib/src/elements/debugger.dart
@@ -902,6 +902,7 @@ class IsolateCommand extends DebuggerCommand {
   IsolateCommand(Debugger debugger) : super(debugger, 'isolate', [
     new IsolateListCommand(debugger),
     new IsolateNameCommand(debugger),
+    new IsolateReloadCommand(debugger),
   ]) {
     alias = 'i';
   }
@@ -962,10 +963,10 @@ class IsolateCommand extends DebuggerCommand {
     }
     return new Future.value(result);
   }
-  String helpShort = 'Switch the current isolate';
+  String helpShort = 'Switch, list, rename, or reload isolates';
 
   String helpLong =
-      'Switch, list, or rename isolates.\n'
+      'Switch the current isolate.\n'
       '\n'
       'Syntax: isolate <number>\n'
       '        isolate <name>\n';
@@ -1042,14 +1043,36 @@ class IsolateNameCommand extends DebuggerCommand {
     return debugger.isolate.setName(args[0]);
   }
 
-  String helpShort = 'Rename an isolate';
+  String helpShort = 'Rename the current isolate';
 
   String helpLong =
-      'Rename an isolate.\n'
+      'Rename the current isolate.\n'
       '\n'
       'Syntax: isolate name <name>\n';
 }
 
+class IsolateReloadCommand extends DebuggerCommand {
+  IsolateReloadCommand(Debugger debugger) : super(debugger, 'reload', []);
+
+  Future run(List<String> args) async {
+    if (debugger.isolate == null) {
+      debugger.console.print('There is no current vm');
+      return;
+    }
+
+    await debugger.isolate.reloadSources();
+
+    debugger.console.print('Isolate reloading....');
+  }
+
+  String helpShort = 'Reload the sources for the current isolate.';
+
+  String helpLong =
+      'Reload the sources for the current isolate.\n'
+      '\n'
+      'Syntax: reload\n';
+}
+
 class InfoCommand extends DebuggerCommand {
   InfoCommand(Debugger debugger) : super(debugger, 'info', [
       new InfoBreakpointsCommand(debugger),
@@ -1650,6 +1673,15 @@ class ObservatoryDebugger extends Debugger {
         console.print("Isolate ${iso.number} renamed to '${iso.name}'");
         break;
 
+      case ServiceEvent.kIsolateReload:
+        var reloadError = event.reloadError;
+        if (reloadError != null) {
+          console.print('Isolate reload failed: ${event.reloadError}');
+        } else {
+          console.print('Isolate reloaded.');
+        }
+        break;
+
       case ServiceEvent.kPauseStart:
       case ServiceEvent.kPauseExit:
       case ServiceEvent.kPauseBreakpoint: