internal/pkgbits: cleanup pre-Go 1.17 workaround

Now that golang/go#44505 is resolved, we can simplify frames_go1*.go.

This was already done in GOROOT in https://go.dev/cl/420903.

Change-Id: Ia7f2a123794fad62532bae2da267b0c8034917bc
Reviewed-on: https://go-review.googlesource.com/c/tools/+/609955
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>

internal/pkgbits/frames_go1.go

diff --git a/internal/pkgbits/frames_go1.go b/internal/pkgbits/frames_go1.go
deleted file mode 100644
index 5294f6a..0000000
--- a/internal/pkgbits/frames_go1.go
+++ /dev/null
@@ -1,21 +0,0 @@
-// Copyright 2021 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build !go1.7
-// +build !go1.7
-
-// TODO(mdempsky): Remove after #44505 is resolved
-
-package pkgbits
-
-import "runtime"
-
-func walkFrames(pcs []uintptr, visit frameVisitor) {
-	for _, pc := range pcs {
-		fn := runtime.FuncForPC(pc)
-		file, line := fn.FileLine(pc)
-
-		visit(file, line, fn.Name(), pc-fn.Entry())
-	}
-}

internal/pkgbits/frames_go17.go

diff --git a/internal/pkgbits/frames_go17.go b/internal/pkgbits/frames_go17.go
deleted file mode 100644
index 2324ae7..0000000
--- a/internal/pkgbits/frames_go17.go
+++ /dev/null
@@ -1,28 +0,0 @@
-// Copyright 2021 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build go1.7
-// +build go1.7
-
-package pkgbits
-
-import "runtime"
-
-// walkFrames calls visit for each call frame represented by pcs.
-//
-// pcs should be a slice of PCs, as returned by runtime.Callers.
-func walkFrames(pcs []uintptr, visit frameVisitor) {
-	if len(pcs) == 0 {
-		return
-	}
-
-	frames := runtime.CallersFrames(pcs)
-	for {
-		frame, more := frames.Next()
-		visit(frame.File, frame.Line, frame.Function, frame.PC-frame.Entry)
-		if !more {
-			return
-		}
-	}
-}

internal/pkgbits/sync.go

diff --git a/internal/pkgbits/sync.go b/internal/pkgbits/sync.go
index a17a008..1520b73 100644
--- a/internal/pkgbits/sync.go
+++ b/internal/pkgbits/sync.go
@@ -6,6 +6,7 @@
 
 import (
 	"fmt"
+	"runtime"
 	"strings"
 )
 
@@ -23,6 +24,24 @@
 
 type frameVisitor func(file string, line int, name string, offset uintptr)
 
+// walkFrames calls visit for each call frame represented by pcs.
+//
+// pcs should be a slice of PCs, as returned by runtime.Callers.
+func walkFrames(pcs []uintptr, visit frameVisitor) {
+	if len(pcs) == 0 {
+		return
+	}
+
+	frames := runtime.CallersFrames(pcs)
+	for {
+		frame, more := frames.Next()
+		visit(frame.File, frame.Line, frame.Function, frame.PC-frame.Entry)
+		if !more {
+			return
+		}
+	}
+}
+
 // SyncMarker is an enum type that represents markers that may be
 // written to export data to ensure the reader and writer stay
 // synchronized.