Support pixel local storage on ES 3.0 Now that the application-facing API is implemented, we don't have to rely on ES 3.1 anymore. Expose and test the extension on ES 3.0. Bug: angleproject:7279 Change-Id: I5635620b9088201c20bafd283813092a329225d6 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3915327 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Chris Dalton <chris@rive.app> Reviewed-by: Kenneth Russell <kbr@chromium.org> Commit-Queue: Chris Dalton <chris@rive.app>