Auto merge of #11534 - izgzhen:add-blob-url-store, r=Manishearth

Add Blob URL store

Spec: https://w3c.github.io/FileAPI/#BlobURLStore.

I finally decide to put the store under `ScriptThread` and interpret the "global object" as the script thread itself. The new APIs will be used during the page loading (if scheme is `blob`) and `URL.createObjectURL/revokeObjectURL`.

Related to #11131.

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