Add a few more known non-null cases

lib/runtime/dart/_isolate_helper.js

 dart_library.library('dart/_isolate_helper', null, /* Imports */[
   'dart/_runtime',
   'dart/core',
   'dart/_native_typed_data',
   'dart/_interceptors',
   'dart/_js_helper',
   'dart/isolate',
   'dart/_foreign_helper',
   'dart/_js_embedded_names',
   'dart/collection',
@@ skipping 603 matching lines @@
       dart.dsend(this[_scheduledControlEvents], 'addLast', dart.bind(this, 'kill'));
     }
     addErrorListener(port) {
       this.errorPorts.add(port);
     }
     removeErrorListener(port) {
       this.errorPorts.remove(port);
     }
     handleUncaughtError(error, stackTrace) {
       if (dart.notNull(this.errorPorts.isEmpty)) {
-        if (dart.notNull(this.errorsAreFatal) && dart.notNull(core.identical(this, exports._globalState.rootContext))) {
+        if (dart.notNull(this.errorsAreFatal) && core.identical(this, exports._globalState.rootContext)) {
           return;
         }
         if (self.console && self.console.error) {
           self.console.error(error, stackTrace);
         } else {
           core.print(error);
           if (stackTrace != null) core.print(stackTrace);
         }
         return;
       }
       let message = core.List.new(2);
       message[dartx.set](0, dart.toString(error));
       message[dartx.set](1, stackTrace == null ? null : dart.toString(stackTrace));
       for (let port of this.errorPorts)
         port.send(message);
     }
     eval(code) {
       let old = exports._globalState.currentContext;
       exports._globalState.currentContext = this;
       this[_setGlobals]();
       let result = null;
       this[_isExecutingEvent] = true;
       try {
         result = dart.dcall(code);
       } catch (e) {
         let s = dart.stackTrace(e);
         this.handleUncaughtError(e, s);
         if (dart.notNull(this.errorsAreFatal)) {
           this.kill();
-          if (dart.notNull(core.identical(this, exports._globalState.rootContext))) {
+          if (core.identical(this, exports._globalState.rootContext)) {
             throw e;
           }
         }
       }
  finally {
         this[_isExecutingEvent] = false;
         exports._globalState.currentContext = old;
         if (old != null) old[_setGlobals]();
         if (this[_scheduledControlEvents] != null) {
           while (dart.notNull(dart.as(dart.dload(this[_scheduledControlEvents], 'isNotEmpty'), core.bool))) {
@@ skipping 815 matching lines @@
       hash = dart.notNull(hash) >> 0 ^ (dart.notNull(hash) / 4294967296)[dartx.truncate]();
       hash = ~dart.notNull(hash) + (dart.notNull(hash) << 15) & 4294967295;
       hash = dart.notNull(hash) ^ dart.notNull(hash) >> 12;
       hash = dart.notNull(hash) * 5 & 4294967295;
       hash = dart.notNull(hash) ^ dart.notNull(hash) >> 4;
       hash = dart.notNull(hash) * 2057 & 4294967295;
       hash = dart.notNull(hash) ^ dart.notNull(hash) >> 16;
       return hash;
     }
     ['=='](other) {
-      if (dart.notNull(core.identical(other, this))) return true;
+      if (core.identical(other, this)) return true;
       if (dart.is(other, CapabilityImpl)) {
         return core.identical(this[_id], other[_id]);
       }
       return false;
     }
   }
   CapabilityImpl[dart.implements] = () => [isolate.Capability];
   dart.defineNamedConstructor(CapabilityImpl, '_internal');
   dart.setSignature(CapabilityImpl, {
     constructors: () => ({
       CapabilityImpl: [CapabilityImpl, []],
       _internal: [CapabilityImpl, [core.int]]
     }),
     methods: () => ({'==': [core.bool, [core.Object]]})
   });
   // Exports:
   exports.enterJsAsync = enterJsAsync;
   exports.leaveJsAsync = leaveJsAsync;
   exports.isWorker = isWorker;
   exports.startRootIsolate = startRootIsolate;
   exports.IsolateNatives = IsolateNatives;
   exports.RawReceivePortImpl = RawReceivePortImpl;
   exports.ReceivePortImpl = ReceivePortImpl;
   exports.TimerImpl = TimerImpl;
   exports.hasTimer = hasTimer;
   exports.CapabilityImpl = CapabilityImpl;
 });