Generate build timing metrics to proto format file

Test: Dumped the text formated based metrics file to out dir,
and checked the file.
Bug: b/63815990

Change-Id: Iff476f72a0be74eb53b6b26ef468d11c0f24a404

ui/metrics/time.go

@@ -0,0 +1,71 @@
+// Copyright 2018 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package metrics
+
+import (
+	"time"
+
+	"android/soong/ui/metrics/metrics_proto"
+	"android/soong/ui/tracer"
+)
+
+type timeEvent struct {
+	desc string
+	name string
+
+	atNanos uint64 // timestamp measured in nanoseconds since the reference date
+}
+
+type TimeTracer interface {
+	Begin(name, desc string, thread tracer.Thread)
+	End(thread tracer.Thread) metrics_proto.PerfInfo
+}
+
+type timeTracerImpl struct {
+	activeEvents []timeEvent
+}
+
+var _ TimeTracer = &timeTracerImpl{}
+
+func (t *timeTracerImpl) now() uint64 {
+	return uint64(time.Now().UnixNano())
+}
+
+func (t *timeTracerImpl) Begin(name, desc string, thread tracer.Thread) {
+	t.beginAt(name, desc, t.now())
+}
+
+func (t *timeTracerImpl) beginAt(name, desc string, atNanos uint64) {
+	t.activeEvents = append(t.activeEvents, timeEvent{name: name, desc: desc, atNanos: atNanos})
+}
+
+func (t *timeTracerImpl) End(thread tracer.Thread) metrics_proto.PerfInfo {
+	return t.endAt(t.now())
+}
+
+func (t *timeTracerImpl) endAt(atNanos uint64) metrics_proto.PerfInfo {
+	if len(t.activeEvents) < 1 {
+		panic("Internal error: No pending events for endAt to end!")
+	}
+	lastEvent := t.activeEvents[len(t.activeEvents)-1]
+	t.activeEvents = t.activeEvents[:len(t.activeEvents)-1]
+	realTime := atNanos - lastEvent.atNanos
+
+	return metrics_proto.PerfInfo{
+		Desc:      &lastEvent.desc,
+		Name:      &lastEvent.name,
+		StartTime: &lastEvent.atNanos,
+		RealTime:  &realTime}
+}