Fix #415: cherry pick from mozilla master: Bug 1266628 - Duplicate characters will be input when using original Simplified Chinese and Japanese keyboards (#1758)
Fix #415: cherry pick from mozilla master:
Bug 1266628 - Duplicate characters will be input when using original Simplified Chinese and Japanese keyboards (#1758)

brave/browser-ios,Allow2CEO/browser-ios,Allow2CEO/browser-ios,Allow2CEO/browser-ios,Allow2CEO/browser-ios,brave/browser-ios,brave/browser-ios,brave/browser-ios,brave/browser-ios,brave/browser-ios,Allow2CEO/browser-ios,brave/browser-ios,Allow2CEO/browser-ios,Allow2CEO/browser-ios,brave/browser-ios,Allow2CEO/browser-ios,brave/browser-ios