Support upload asset with large file size

[Steven Chan]

The sdk is using volley multipart to upload file, which does not handle large file well. See google/volley#106.

But the sdk can still handle large file better. Currently, an Asset object only accepts byte[] in constructor, which force developer to put the whole file data in memory.

To solve this problem, Asset should also accept being constructed with input stream / uri with a content resolver.

Case 1: byte[]

• Asset size = length of the byte array
• When upload,
  • write the byte array to a temporary file
  • add the file to the multipart request

Case 2: InputStream

• Asset size = given when the Asset object is constructed
• When upload,
  • pipe the data from input stream to a temporary file <- unless volley support piping it to the request directly
  • add the file to the multipart request

Case 3: Uri with ContentResolver

Get a InputStream using the uri and content resolver when needed.

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Update:

InputStream is too low level and we need file size when save asset which is not provided by the stream, we may support Uri (or maybe File and URL later).