Update the common cube map texture in MipmapTest In MipmapTest, mTextureCube is defined so that one side is set to blue. However, the other sides are not explicitly defined. This seems to be causing capture/replay errors due to context mismatch after updating the image memory allocation method to use VMA. (CL: https://crrev.com/c/4191202) * Added definition for the other sides of mTextureCube, now set to white. Bug: b/267811497 Change-Id: Icaca67ba6032e5156c9f4bbf3913459d863c2f1d Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4264172 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Cody Northrop <cnorthrop@google.com> Commit-Queue: Amirali Abdolrashidi <abdolrashidi@google.com>