Clean up some nits in base::NativeLibrary.

base/native_library_ios.mm

Index: base/native_library_ios.mm
diff --git a/base/native_library_ios.mm b/base/native_library_ios.mm
index 60a11f2b4600f7d6bf9b3392c7769280fa839379..6ae7580d48d704882a0b2b7f65e6ae47e7a87a2f 100644
--- a/base/native_library_ios.mm
+++ b/base/native_library_ios.mm
@@ -29,14 +29,14 @@ void UnloadNativeLibrary(NativeLibrary library) {
 
 // static
 void* GetFunctionPointerFromNativeLibrary(NativeLibrary library,
-                                          const char* name) {
+                                          StringPiece name) {
   NOTIMPLEMENTED();
   return nullptr;
 }
 
 // static
-string16 GetNativeLibraryName(const string16& name) {
-  return name;
+string16 GetNativeLibraryName(StringPiece16 name) {
+  return name.as_string();
 }
 
 }  // namespace base