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This CL changes linear resampling to scroll predictor's default predictor
type and also fix related unit tests.
This is to prepare the enabling of scroll resampling. So when the flag
turn on, it will default to use linear resampling predictor type.

This is to get a better scroll experience on scrolling, detail see the doc:
https://docs.google.com/document/d/1KrlQ0m5Ty9RKE1IorjEXDldYFJvUV_Ww10lnjh-TRN0/

Bug: 1000682
Change-Id: I3928428700a36f8c25ac2c0c1294b3a4478bc579
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1786868
Commit-Queue: Ella Ge <eirage@chromium.org>
Reviewed-by: David Bokan <bokan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#697065}