Bug 865649 part.1 Implement KeyboardEvent.code r=smaug
Bug 865649 part.2 Set KeyboardEvent.code value on Windows r=smaug+jimm
Bug 865649 part.3 Set KeyboardEvent.code value on Mac r=smaug+smichaud
Bug 865649 part.4 Set KeyboardEvent.code value on Linux r=smaug+karlt+romaxa
Bug 865649 part.5 Set KeyboardEvent.code value on Android and Gonk r=smaug+nchen+mwu