bind: add missing unsafe import in generated code

The ClassGen.genGo function always uses unsafe, contrary to what
the check in GenGo says. With this CL, generated code always
imports unsafe if there are any classes to be generated.

Change-Id: Ic807111a26e494b4941790830b1950bb8b1f73d5
Reviewed-on: https://go-review.googlesource.com/29873
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>

bind/genclasses.go

@@ -162,18 +162,16 @@ func (g *ClassGen) GenPackage(idx int) {
 
 func (g *ClassGen) GenGo() {
 	g.Printf(classesGoHeader)
-	impUnsafe := false
 	for _, cls := range g.classes {
 		for _, f := range cls.Funcs {
 			if f.Public && g.isFuncSupported(f) {
-				impUnsafe = true
 				pkgName := strings.Replace(cls.Name, ".", "/", -1)
 				g.Printf("import %q\n", "Java/"+pkgName)
 				break
 			}
 		}
 	}
-	if impUnsafe {
+	if len(g.classes) > 0 {
 		g.Printf("import \"unsafe\"\n\n")
 	}
 	g.Printf("type proxy interface { Bind_proxy_refnum__() int32 }\n\n")

bind/testdata/classes.go.golden

@@ -44,6 +44,8 @@ import (
 	_seq "golang.org/x/mobile/bind/seq"
 )
 
+import "unsafe"
+
 type proxy interface { Bind_proxy_refnum__() int32 }
 
 // Suppress unused package error

bind/testdata/java.go.golden

@@ -39,6 +39,8 @@ import (
 	_seq "golang.org/x/mobile/bind/seq"
 )
 
+import "unsafe"
+
 type proxy interface { Bind_proxy_refnum__() int32 }
 
 // Suppress unused package error