Add method GetKeyFromSystem to WiFiService on Windows and Mac.

components/wifi/wifi_test.cc

Index: components/wifi/wifi_test.cc
diff --git a/components/wifi/wifi_test.cc b/components/wifi/wifi_test.cc
index f5d14bb580c7ae26e70fc695d23f7a252a72c1b5..089774579f5bdfc0e9871f4459a02c34b2ba2ebe 100644
--- a/components/wifi/wifi_test.cc
+++ b/components/wifi/wifi_test.cc
@@ -66,6 +66,7 @@ WiFiTest::Result WiFiTest::Main(int argc, const char* argv[]) {
   if (!ParseCommandLine(argc, argv)) {
     VLOG(0) <<  "Usage: " << argv[0] <<
                 " [--list]"
+                " [--get_key]"
                 " [--get_properties]"
                 " [--create]"
                 " [--connect]"
@@ -190,6 +191,18 @@ bool WiFiTest::ParseCommandLine(int argc, const char* argv[]) {
     }
   }
 
+  if (parsed_command_line.HasSwitch("get_key")) {
+    if (network_guid.length() > 0) {
+      std::string error;
+      std::string key_data;
+      wifi_service->GetKeyFromSystem(network_guid,
+                                     &key_data,
+                                     &error);
+      VLOG(0) << key_data << error;
+      return true;
+    }
+  }
+
   return false;
 }