Linear filter for texture object in 2d context

This is a temporary fix to enforce linear filter for texture object
in OffscreenCanvasRenderingContext2D in commit(). An ideal solution, which is
not urgent for OffscreenCanvas launch, is to adapt the filter to respect
image-rendering CSS property, as indicated in crbug.com/645590.

BUG=676666
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel;master.tryserver.chromium.android:android_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2607373002
Cr-Commit-Position: refs/heads/master@{#442803}
3 files changed