Initialize View Start Time During View Registration (#1215)

* Initialize view start time during view registration

* Remove unnecessary start time initialization from reportUsage

* Remove unnecessary start time check in toMetric

stats/view/worker.go

diff --git a/stats/view/worker.go b/stats/view/worker.go
index 51be9e2..ab8bfd4 100644
--- a/stats/view/worker.go
+++ b/stats/view/worker.go
@@ -277,7 +277,7 @@
 		case cmd := <-w.c:
 			cmd.handleCommand(w)
 		case <-w.timer.C:
-			w.reportUsage(time.Now())
+			w.reportUsage()
 		case <-w.quit:
 			w.timer.Stop()
 			close(w.c)
@@ -324,6 +324,7 @@
 		return x, nil
 	}
 	w.views[vi.view.Name] = vi
+	w.startTimes[vi] = time.Now()
 	ref := w.getMeasureRef(vi.view.Measure.Name())
 	ref.views[vi] = struct{}{}
 	return vi, nil
@@ -333,20 +334,17 @@
 	w.mu.Lock()
 	defer w.mu.Unlock()
 	delete(w.views, v.view.Name)
+	delete(w.startTimes, v)
 	if measure := w.measures[v.view.Measure.Name()]; measure != nil {
 		delete(measure.views, v)
 	}
 }
 
-func (w *worker) reportView(v *viewInternal, now time.Time) {
+func (w *worker) reportView(v *viewInternal) {
 	if !v.isSubscribed() {
 		return
 	}
 	rows := v.collectedRows()
-	_, ok := w.startTimes[v]
-	if !ok {
-		w.startTimes[v] = now
-	}
 	viewData := &Data{
 		View:  v.view,
 		Start: w.startTimes[v],
@@ -360,11 +358,11 @@
 	}
 }
 
-func (w *worker) reportUsage(now time.Time) {
+func (w *worker) reportUsage() {
 	w.mu.Lock()
 	defer w.mu.Unlock()
 	for _, v := range w.views {
-		w.reportView(v, now)
+		w.reportView(v)
 	}
 }
 
@@ -373,11 +371,6 @@
 		return nil
 	}
 
-	_, ok := w.startTimes[v]
-	if !ok {
-		w.startTimes[v] = now
-	}
-
 	var startTime time.Time
 	if v.metricDescriptor.Type == metricdata.TypeGaugeInt64 ||
 		v.metricDescriptor.Type == metricdata.TypeGaugeFloat64 {

stats/view/worker_commands.go

diff --git a/stats/view/worker_commands.go b/stats/view/worker_commands.go
index e4a2fbd..9ac4cc0 100644
--- a/stats/view/worker_commands.go
+++ b/stats/view/worker_commands.go
@@ -95,7 +95,7 @@
 		}
 
 		// Report pending data for this view before removing it.
-		w.reportView(vi, time.Now())
+		w.reportView(vi)
 
 		vi.unsubscribe()
 		if !vi.isSubscribed() {