FrameCapture: Skip invalid VertexAttribPointer calls in MEC. In CaptureVertexArrayState when a non-default VAO is bound and no GL_ARRAY_BUFFER is bound, VertexAttribPointer calls with a non-null offset are invalid and will produce: "Client data cannot be used with a non-default vertex array object." Add a test that leaves a vertex array with an invalid vertex attribute pointer and used to produce an invalid trace with MEC. Test: angle_end2end_tests --gtest_filter="VertexAttributeTestES3.InvalidAttribPointer/*" Bug: angleproject:7042 Bug: angleproject:7098 Change-Id: Iaf91fe7f191c44df79db47bb5455e5df922f2ed5 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3475353 Reviewed-by: Cody Northrop <cnorthrop@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Lubosz Sarnecki <lubosz.sarnecki@collabora.com>