Revert "Add ticks counter to Timer."

sdk/lib/_internal/js_runtime/lib/isolate_helper.dart

Index: sdk/lib/_internal/js_runtime/lib/isolate_helper.dart
diff --git a/sdk/lib/_internal/js_runtime/lib/isolate_helper.dart b/sdk/lib/_internal/js_runtime/lib/isolate_helper.dart
index 856a442bfec9452bd8d9e59b4028fd6d7adf0638..c12a746848bbc09d5bb255ba60978763ce08824d 100644
--- a/sdk/lib/_internal/js_runtime/lib/isolate_helper.dart
+++ b/sdk/lib/_internal/js_runtime/lib/isolate_helper.dart
@@ -1366,7 +1366,6 @@ class TimerImpl implements Timer {
   final bool _once;
   bool _inEventLoop = false;
   int _handle;
-  int _tick = 0;
 
   TimerImpl(int milliseconds, void callback()) : _once = true {
     if (milliseconds == 0 && (!hasTimer() || _globalState.isWorker)) {
@@ -1392,7 +1391,6 @@ class TimerImpl implements Timer {
       void internalCallback() {
         _handle = null;
         leaveJsAsync();
-        this._tick = 1;
         callback();
       }
 
@@ -1410,19 +1408,10 @@ class TimerImpl implements Timer {
       : _once = false {
     if (hasTimer()) {
       enterJsAsync();
-      int start = JS('int', 'Date.now()');
       _handle = JS(
           'int',
           'self.setInterval(#, #)',
           convertDartClosureToJS(() {
-            int tick = this._tick + 1;
-            if (milliseconds > 0) {
-              int duration = JS('int', 'Date.now()') - start;
-              if (duration > (tick + 1) * milliseconds) {
-                tick = duration ~/ milliseconds;
-              }
-            }
-            this._tick = tick;
             callback(this);
           }, 0),
           milliseconds);
@@ -1431,8 +1420,6 @@ class TimerImpl implements Timer {
     }
   }
 
-  int get tick => _tick;
-
   void cancel() {
     if (hasTimer()) {
       if (_inEventLoop) {