Fix some warnings in the example plugin.
Fix some warnings in the example plugin.

TEST=none
BUG=none
siweilvxing/ppapi,dingdayong/ppapi,cacpssl/ppapi,tiaolong/ppapi,thdtjsdn/ppapi,phisixersai/ppapi,tonyjoule/ppapi,xiaozihui/ppapi,siweilvxing/ppapi,stefanie924/ppapi,siweilvxing/ppapi,rise-worlds/ppapi,gwobay/ppapi,nanox/ppapi,nanox/ppapi,dralves/ppapi,cacpssl/ppapi,huochetou999/ppapi,JustRight/ppapi,qwop/ppapi,lag945/ppapi,chenfeng8742/ppapi,ruder/ppapi,Xelemsta/ppapi,c1soju96/ppapi,chenfeng8742/ppapi,xinghaizhou/ppapi,tonyjoule/ppapi,dingdayong/ppapi,fubaydullaev/ppapi,huochetou999/ppapi,phisixersai/ppapi,nanox/ppapi,dralves/ppapi,Xelemsta/ppapi,YachaoLiu/ppapi,dralves/ppapi,HAfsari/ppapi,Xelemsta/ppapi,gwobay/ppapi,nanox/ppapi,qwop/ppapi,dralves/ppapi,Xelemsta/ppapi,ruder/ppapi,c1soju96/ppapi,phisixersai/ppapi,dingdayong/ppapi,huqingyu/ppapi,whitewolfm/ppapi,xinghaizhou/ppapi,stefanie924/ppapi,chenfeng8742/ppapi,YachaoLiu/ppapi,whitewolfm/ppapi,huqingyu/ppapi,gwobay/ppapi,tiaolong/ppapi,xinghaizhou/ppapi,xiaozihui/ppapi,CharlesHuimin/ppapi,fubaydullaev/ppapi,xiaozihui/ppapi,tiaolong/ppapi,HAfsari/ppapi,huochetou999/ppapi,qwop/ppapi,tiaolong/ppapi,whitewolfm/ppapi,JustRight/ppapi,lag945/ppapi,whitewolfm/ppapi,Xelemsta/ppapi,fubaydullaev/ppapi,xinghaizhou/ppapi,YachaoLiu/ppapi,CharlesHuimin/ppapi,siweilvxing/ppapi,cacpssl/ppapi,xiaozihui/ppapi,rise-worlds/ppapi,stefanie924/ppapi,tonyjoule/ppapi,HAfsari/ppapi,c1soju96/ppapi,nanox/ppapi,qwop/ppapi,xuesongzhu/ppapi,thdtjsdn/ppapi,huqingyu/ppapi,CharlesHuimin/ppapi,huqingyu/ppapi,chenfeng8742/ppapi,rise-worlds/ppapi,phisixersai/ppapi,thdtjsdn/ppapi,dralves/ppapi,tonyjoule/ppapi,thdtjsdn/ppapi,huqingyu/ppapi,JustRight/ppapi,HAfsari/ppapi,xuesongzhu/ppapi,tiaolong/ppapi,fubaydullaev/ppapi,cacpssl/ppapi,xuesongzhu/ppapi,rise-worlds/ppapi,huochetou999/ppapi,CharlesHuimin/ppapi,gwobay/ppapi,ruder/ppapi,phisixersai/ppapi,huochetou999/ppapi,thdtjsdn/ppapi,chenfeng8742/ppapi,lag945/ppapi,qwop/ppapi,lag945/ppapi,CharlesHuimin/ppapi,fubaydullaev/ppapi,YachaoLiu/ppapi,c1soju96/ppapi,YachaoLiu/ppapi,siweilvxing/ppapi,stefanie924/ppapi,whitewolfm/ppapi,gwobay/ppapi,ruder/ppapi,rise-worlds/ppapi,xinghaizhou/ppapi,HAfsari/ppapi,xuesongzhu/ppapi,xiaozihui/ppapi,JustRight/ppapi,dingdayong/ppapi,xuesongzhu/ppapi,cacpssl/ppapi,ruder/ppapi,tonyjoule/ppapi,stefanie924/ppapi,lag945/ppapi,dingdayong/ppapi,JustRight/ppapi,c1soju96/ppapi