Fix some review comments and make Binutils mutex private. (#238)

internal/binutils/binutils.go

 
 // A Binutils implements plugin.ObjTool by invoking the GNU binutils.
 type Binutils struct {
-	sync.Mutex
+	mu  sync.Mutex
 	rep *binrep
 }
 
 
 // get returns the current representation for bu, initializing it if necessary.
 func (bu *Binutils) get() *binrep {
-	bu.Mutex.Lock()
+	bu.mu.Lock()
 	r := bu.rep
 	if r == nil {
 		r = &binrep{}
 		initTools(r, "")
 		bu.rep = r
 	}
-	bu.Mutex.Unlock()
+	bu.mu.Unlock()
 	return r
 }
 
 // update modifies the rep for bu via the supplied function.
 func (bu *Binutils) update(fn func(r *binrep)) {
 	r := &binrep{}
-	bu.Mutex.Lock()
-	defer bu.Mutex.Unlock()
+	bu.mu.Lock()
+	defer bu.mu.Unlock()
 	if bu.rep == nil {
 		initTools(r, "")
 	} else {

internal/report/source_test.go

 )
 
 func TestWebList(t *testing.T) {
-	if runtime.GOOS != "linux" {
-		t.Skip("weblist only tested on linux")
+	if runtime.GOOS != "linux" || runtime.GOARCH != "amd64" {
+		t.Skip("weblist only tested on x86-64 linux")
 	}
 
 	cpu := readProfile(filepath.Join("testdata", "sample.cpu"), t)
 
 func TestIndentation(t *testing.T) {
 	for _, c := range []struct {
-		str    string
-		indent int
+		str        string
+		wantIndent int
 	}{
 		{"", 0},
 		{"foobar", 0},
 		{"       \tfoo", 8},
 		{"        \tfoo", 16},
 	} {
-		if n := indentation(c.str); n != c.indent {
-			t.Errorf("indentation for %v: expect %d, got %d\n", c.str, c.indent, n)
+		if n := indentation(c.str); n != c.wantIndent {
+			t.Errorf("indentation(%v): got %d, want %d", c.str, n, c.wantIndent)
 		}
 	}
 }