In version 2.0 a new feature was added instant-run.
To enable this feature tool adds a lots of meta information, so the first build and upload takes more time.
Be aware about
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setting minSdkVersion 15 or higher to get any profit;
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Instant Run does not currently work with Jack (to support java 8) and will be disabled while using the new toolchain;
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you may still encounter some glitches and bugs;
Here we can write (or vote) issues (report to make the better tool).