When cloning into an SkPicture, clear its data.
When cloning into an SkPicture, clear its data.

Prevents a memory leak if the caller clones into an SkPicture
that already has a playback or record.

Review URL: https://codereview.appspot.com/6813081

git-svn-id: e8541e15acce502a64c929015570ad1648e548cd@6282 2bbb7eff-a529-9590-31e7-b0007b416f81

Hankuo/color-emoji.skia,Frankie-666/color-emoji.skia,hbwhlklive/color-emoji.skia,Hankuo/color-emoji.skia,Frankie-666/color-emoji.skia,MatChung/color-emoji.skia,Frankie-666/color-emoji.skia,Hankuo/color-emoji.skia,MatChung/color-emoji.skia,MatChung/color-emoji.skia,Frankie-666/color-emoji.skia,Frankie-666/color-emoji.skia,MatChung/color-emoji.skia,MatChung/color-emoji.skia,Hankuo/color-emoji.skia,Frankie-666/color-emoji.skia,hbwhlklive/color-emoji.skia,hbwhlklive/color-emoji.skia,Hankuo/color-emoji.skia,hbwhlklive/color-emoji.skia,MatChung/color-emoji.skia,hbwhlklive/color-emoji.skia,hbwhlklive/color-emoji.skia,Hankuo/color-emoji.skia