Fix Animation on Safari

Fix Animation issue in the LESS file :)

build/less/dropdown.less

@@ -295,27 +295,27 @@
 }
 @-webkit-keyframes flipInX {
   0% {
-    transform: perspective(400px) rotate3d(1, 0, 0, 90deg);
-    transition-timing-function: ease-in;
+    -webkit-transform: perspective(400px) rotate3d(1, 0, 0, 90deg);
+    -webkit-transition-timing-function: ease-in;
     opacity: 0;
   }
 
   40% {
-    transform: perspective(400px) rotate3d(1, 0, 0, -20deg);
-    transition-timing-function: ease-in;
+    -webkit-transform: perspective(400px) rotate3d(1, 0, 0, -20deg);
+    -webkit-transition-timing-function: ease-in;
   }
 
   60% {
-    transform: perspective(400px) rotate3d(1, 0, 0, 10deg);
+    -webkit-transform: perspective(400px) rotate3d(1, 0, 0, 10deg);
     opacity: 1;
   }
 
   80% {
-    transform: perspective(400px) rotate3d(1, 0, 0, -5deg);
+    -webkit-transform: perspective(400px) rotate3d(1, 0, 0, -5deg);
   }
 
   100% {
-    transform: perspective(400px);
+    -webkit-transform: perspective(400px);
   }
 }
 
@@ -344,4 +344,4 @@
       }
     }
   }
-}
+}