pagetrace: fix build when experiment is on

due to a recent change, this experiment does not compile at all. This
simply fixes to pass in the new required parameter.

Change-Id: Idce0e72fa436a7acf4923717913deb3a37847fe2
Reviewed-on: https://go-review.googlesource.com/c/go/+/551415
Auto-Submit: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/runtime/pagetrace_on.go

@@ -317,7 +317,7 @@ func finishPageTrace() {
 		pageTrace.enabled = false
 
 		// Execute a ragged barrier, flushing each trace buffer.
-		forEachP(func(pp *p) {
+		forEachP(waitReasonPageTraceFlush, func(pp *p) {
 			if pp.pageTraceBuf.buf != nil {
 				pp.pageTraceBuf = pp.pageTraceBuf.flush(pp.id, nanotime())
 			}

src/runtime/runtime2.go

@@ -1127,6 +1127,7 @@ const (
 	waitReasonFlushProcCaches                         // "flushing proc caches"
 	waitReasonTraceGoroutineStatus                    // "trace goroutine status"
 	waitReasonTraceProcStatus                         // "trace proc status"
+	waitReasonPageTraceFlush                          // "page trace flush"
 	waitReasonCoroutine                               // "coroutine"
 )
 
@@ -1166,6 +1167,7 @@ var waitReasonStrings = [...]string{
 	waitReasonFlushProcCaches:       "flushing proc caches",
 	waitReasonTraceGoroutineStatus:  "trace goroutine status",
 	waitReasonTraceProcStatus:       "trace proc status",
+	waitReasonPageTraceFlush:        "page trace flush",
 	waitReasonCoroutine:             "coroutine",
 }
 

src/runtime/trace2status.go

@@ -147,6 +147,7 @@ func goStatusToTraceGoStatus(status uint32, wr waitReason) traceGoStatus {
 			wr == waitReasonGCMarkTermination ||
 			wr == waitReasonGarbageCollection ||
 			wr == waitReasonTraceProcStatus ||
+			wr == waitReasonPageTraceFlush ||
 			wr == waitReasonGCWorkerActive {
 			tgs = traceGoRunning
 		}