Check interface name before calling CoreWLAN

This change attempts to address some Mac CWInterface crashes.  Although
CWInterface's interfaceWithName was deprecated in 10.10, these crashes
don't appear to be a result of that (especially since there is one other
use of the API in Chromium that isn't experiencing any crashes).  This
change adds a check on the interface name before calling
interfaceWithName to ensure it is only called on Wifi interfaces.

Bug: 827944
Change-Id: I2775bc7c3b26a015c1893b3ba56a13f66f3d5ead
Reviewed-on: https://chromium-review.googlesource.com/1016068Reviewed-by: Derek Cheng <imcheng@chromium.org>
Commit-Queue: Brandon Tolsch <btolsch@chromium.org>
Cr-Commit-Position: refs/heads/master@{#551737}

chrome/browser/media/router/discovery/discovery_network_list_wifi_mac.mm

@@ -5,20 +5,17 @@
 #include "chrome/browser/media/router/discovery/discovery_network_list_wifi.h"
 
 #include <CoreWLAN/CoreWLAN.h>
-#include <string.h>
 
+#include <string>
 #include <utility>
 
 #include "base/logging.h"
-#include "base/mac/scoped_nsobject.h"
 #include "base/strings/sys_string_conversions.h"
 
 namespace media_router {
+namespace {
 
-bool MaybeGetWifiSSID(const std::string& if_name, std::string* ssid_out) {
-  DCHECK(ssid_out);
-
-  NSString* ns_ifname = base::SysUTF8ToNSString(if_name.data());
+bool GetWifiSSID(NSString* ns_ifname, std::string* ssid_out) {
   CWInterface* interface = [CWInterface interfaceWithName:ns_ifname];
   if (interface == nil) {
     return false;
@@ -31,4 +28,17 @@ bool MaybeGetWifiSSID(const std::string& if_name, std::string* ssid_out) {
   return true;
 }
 
+}  // namespace
+
+bool MaybeGetWifiSSID(const std::string& if_name, std::string* ssid_out) {
+  DCHECK(ssid_out);
+
+  NSString* ns_ifname = base::SysUTF8ToNSString(if_name.data());
+  NSSet* all_ifnames = [CWInterface interfaceNames];
+  for (NSString* ifname in all_ifnames)
+    if ([ifname isEqualToString:ns_ifname])
+      return GetWifiSSID(ns_ifname, ssid_out);
+  return false;
+}
+
 }  // namespace media_router