Remove newPinchInterface in gpu benchmarking extension
Remove newPinchInterface in gpu benchmarking extension

This was added in r272359 in 2014, it's safe to remove now.
Note, this needs to land after the check is removed in the
catapult project:

https://codereview.chromium.org/1680653003

BUG=

Review URL: https://codereview.chromium.org/1671413002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#375691}

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