Fix base::GetNativeLibraryName() for Mac.

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 6ae7580d48d704882a0b2b7f65e6ae47e7a87a2f..fb1b077a0f48f3fce82867c199191334683baa00 100644
--- a/base/native_library_ios.mm
+++ b/base/native_library_ios.mm
@@ -6,6 +6,8 @@
 
 #include "base/logging.h"
 
+#include "base/strings/string_util.h"
+
 namespace base {
 
 std::string NativeLibraryLoadError::ToString() const {
@@ -35,7 +37,8 @@ void* GetFunctionPointerFromNativeLibrary(NativeLibrary library,
 }
 
 // static
-string16 GetNativeLibraryName(StringPiece16 name) {
+std::string GetNativeLibraryName(StringPiece name) {
+  DCHECK(IsStringASCII(name));
   return name.as_string();
 }