FrameCapture: Check EXT before limiting tex buffer Only apply the limit to textureBufferOffsetAlignment when the extension is enabled, otherwise the default alignment is zero and the assert will fire. This was missed previously because most of us (including the bots) run with the following GN arg enabled: angle_expose_non_conformant_extensions_and_versions = true Test: FrameCapture on Pixel 4 Bug: b/180418810 Bug: angleproject:5658 Change-Id: Iea0618f439efeb3351300ee5af54066bfe526f71 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3140097 Commit-Queue: Cody Northrop <cnorthrop@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Tim Van Patten <timvp@google.com>