Deprecate FileError in FileAPI

LayoutTests/fast/filesystem/resources/op-remove.js

 var testCases = [
     {
         name: 'RemoveSimple',
         precondition: [
             {fullPath:'/a', isDirectory:true},
             {fullPath:'/b'}
         ],
         tests: [
             function(helper) { helper.remove('/a'); },
             function(helper) { helper.remove('/b'); },
-            function(helper) { helper.remove('/', FileError.INVALID_MODIFICATION_ERR); }
+            function(helper) { helper.remove('/', 'InvalidModificationError'); }
         ],
         postcondition: [
             {fullPath:'/a', nonexistent:true},
             {fullPath:'/b', nonexistent:true}
         ],
     },
     {
         name: 'RemoveNonRecursiveWithChildren',
         precondition: [
             {fullPath:'/a', isDirectory:true},
             {fullPath:'/a/b', isDirectory:true},
             {fullPath:'/a/c',}
         ],
         tests: [
-            function(helper) { helper.remove('/a', FileError.INVALID_MODIFICATION_ERR); }
+            function(helper) { helper.remove('/a', 'InvalidModificationError'); }
         ],
         postcondition: [
             {fullPath:'/a', isDirectory:true},
             {fullPath:'/a/b', isDirectory:true},
             {fullPath:'/a/c',}
         ],
     },
     {
         name: 'RemoveRecursiveWithoutChildren',
         precondition: [
             {fullPath:'/a', isDirectory:true},
         ],
         tests: [
             function(helper) { helper.removeRecursively('/a'); }
         ],
         postcondition: [
             {fullPath:'/a', nonexistent:true},
         ],
     },
     {
         name: 'RemoveRecursiveWithChildren',
         precondition: [
             {fullPath:'/a', isDirectory:true},
             {fullPath:'/a/b', isDirectory:true},
             {fullPath:'/a/c',}
         ],
         tests: [
             function(helper) { helper.removeRecursively('/a'); },
-            function(helper) { helper.removeRecursively('/', FileError.INVALID_MODIFICATION_ERR); }
+            function(helper) { helper.removeRecursively('/', 'InvalidModificationError'); }
         ],
         postcondition: [
             {fullPath:'/a', nonexistent:true},
         ],
     },
 ];