[iOS][MF] Sets the last frame ID

Not setting this was causing a crash on iOS < 11.2

Bug: 878388
Change-Id: I6b5391a360e1f06e584352235a978273d704bd26
Reviewed-on: https://chromium-review.googlesource.com/c/1348034Reviewed-by: Yi Su <mrsuyi@chromium.org>
Commit-Queue: Javier Ernesto Flores Robles <javierrobles@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610405}

ios/chrome/browser/ui/autofill/manual_fill/manual_fill_injection_handler.mm

@@ -200,6 +200,8 @@ const int64_t kJavaScriptExecutionTimeoutInSeconds = 1;
   FormInputAccessoryViewHandler* handler =
       [[FormInputAccessoryViewHandler alloc] init];
   handler.JSSuggestionManager = self.suggestionManager;
+  [handler setLastFocusFormActivityWebFrameID:
+               base::SysUTF8ToNSString(self.lastFocusedElementFrameIdentifier)];
   [handler selectNextElementWithoutButtonPress];
 }