Further optimize babel-generator Buffer
Further optimize babel-generator Buffer

We can eek out a bit more speed from Babel generator by turning the
buffer into an array as well.
Re: #3565

```
Items: 2 , time: 4 length: 114
Items: 4 , time: 3 length: 218
Items: 8 , time: 3 length: 426
Items: 16 , time: 2 length: 861
Items: 32 , time: 5 length: 1741
Items: 64 , time: 2 length: 3501
Items: 128 , time: 4 length: 7106
Items: 256 , time: 8 length: 14530
Items: 512 , time: 12 length: 29378
Items: 1024 , time: 24 length: 59147
Items: 2048 , time: 38 length: 121611
Items: 4096 , time: 71 length: 246539
Items: 8192 , time: 131 length: 496395
Items: 16384 , time: 350 length: 1015260
Items: 32768 , time: 573 length: 2063836
Items: 65536 , time: 1263 length: 4160988
Items: 131072 , time: 2143 length: 8448509
Items: 262144 , time: 4859 length: 17230333
```

to

```
Items: 2 , time: 4 length: 114
Items: 4 , time: 3 length: 218
Items: 8 , time: 9 length: 426
Items: 16 , time: 1 length: 861
Items: 32 , time: 5 length: 1741
Items: 64 , time: 1 length: 3501
Items: 128 , time: 3 length: 7106
Items: 256 , time: 7 length: 14530
Items: 512 , time: 9 length: 29378
Items: 1024 , time: 17 length: 59147
Items: 2048 , time: 30 length: 121611
Items: 4096 , time: 61 length: 246539
Items: 8192 , time: 113 length: 496395
Items: 16384 , time: 307 length: 1015260
Items: 32768 , time: 443 length: 2063836
Items: 65536 , time: 1065 length: 4160988
Items: 131072 , time: 1799 length: 8448509
Items: 262144 , time: 4217 length: 17230333
```

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