iOS full-form Autofill: Handle partially filled forms correctly.

components/autofill/ios/browser/js_autofill_manager.mm

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "components/autofill/ios/browser/js_autofill_manager.h"
 
 #include "base/format_macros.h"
 #include "base/json/string_escape.h"
 #include "base/logging.h"
 
@@ skipping 60 matching lines @@
     completionHandler();
   };
 
   NSString* js =
       [NSString stringWithFormat:@"__gCrWeb.autofill.fillActiveFormField(%@);",
                                  dataString];
   [self evaluate:js stringResultHandler:resultHandler];
 }
 
 - (void)fillForm:(NSString*)dataString
-        styleElements:(BOOL)styleElements
-    completionHandler:(ProceduralBlock)completionHandler {
+         onlyFillEmpty:(BOOL)onlyFillEmpty
+    forceFillFieldName:(NSString*)forceFillFieldName
+         styleElements:(BOOL)styleElements
+     completionHandler:(ProceduralBlock)completionHandler {
   DCHECK(completionHandler);
-  NSString* fillFormJS =
-      [NSString stringWithFormat:@"__gCrWeb.autofill.fillForm(%@, %s);",
-                                 dataString, styleElements ? "true" : "false"];
+  std::string fieldName =
+      forceFillFieldName
+          ? base::GetQuotedJSONString([forceFillFieldName UTF8String])
+          : "null";
+  NSString* fillFormJS = [NSString
+      stringWithFormat:@"__gCrWeb.autofill.fillForm(%@, %s, %s, %s);",
+                       dataString, onlyFillEmpty ? "true" : "false",
+                       fieldName.c_str(), styleElements ? "true" : "false"];
   id stringResultHandler = ^(NSString*, NSError*) {
     completionHandler();
   };
   return [self evaluate:fillFormJS stringResultHandler:stringResultHandler];
 }
 
 - (void)dispatchAutocompleteEvent:(NSString*)formName {
   NSString* dispatchAutocompleteEventJS = [NSString
       stringWithFormat:@"__gCrWeb.autofill.dispatchAutocompleteEvent(%s);",
                        base::GetQuotedJSONString([formName UTF8String])
@@ skipping 12 matching lines @@
 }
 
 - (void)fillPredictionData:(NSString*)dataString {
   [self deferredEvaluate:
             [NSString
                 stringWithFormat:@"__gCrWeb.autofill.fillPredictionData(%@);",
                                  dataString]];
 }
 
 @end