Fix uniform array handling in ProgramGL. Our validation wouldn't correctly handle single-element arrays because it was checking size > 1 instead of isArray(). This caused issues in ProgramGL on some drivers that optimized the array size (AMD) if some elements were unused. BUG=angleproject:882 Change-Id: I417d13cd86380e2c6caa688f6398709a74692e21 Reviewed-on: https://chromium-review.googlesource.com/289201 Reviewed-by: Corentin Wallez <cwallez@chromium.org> Reviewed-by: Brandon Jones <bajones@chromium.org> Tested-by: Geoff Lang <geofflang@chromium.org>