Adds missing import and forward declarations

Bug: 845472
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: Ibe6443cfdb658cce9caf351171f2c23cbff492ed
Reviewed-on: https://chromium-review.googlesource.com/1136634Reviewed-by: Moe Ahmadi <mahmadi@chromium.org>
Commit-Queue: Javier Ernesto Flores Robles <javierrobles@chromium.org>
Cr-Commit-Position: refs/heads/master@{#574935}

ios/chrome/browser/autofill/form_input_accessory_view_provider.h

@@ -5,10 +5,17 @@
 #ifndef IOS_CHROME_BROWSER_AUTOFILL_FORM_INPUT_ACCESSORY_VIEW_PROVIDER_H_
 #define IOS_CHROME_BROWSER_AUTOFILL_FORM_INPUT_ACCESSORY_VIEW_PROVIDER_H_
 
+namespace web {
+struct FormActivityParams;
+class WebState;
+}  // namespace web
+
 @protocol FormInputAccessoryViewDelegate;
 @protocol FormInputAccessoryViewProvider;
 @class FormInputAccessoryViewController;
 
+#import <UIKit/UIKit.h>
+
 // Block type to indicate that a FormInputAccessoryViewProvider has an accessory
 // view to provide.
 typedef void (^AccessoryViewAvailableCompletion)(