Until independence India was a part of the British Empire and Indians were what was known as British Subjects. There was no citizenship criteria for India per se, but the general rule for British subject held good for India as well.
Until 1949 British Subjects was used to refer generally to any person born or naturalized in the United Kingdom or the British Empire. So to be a subject required only that a person be born in any territory under the sovereignty of the Crown. Within Indian territory also, people within the native states were not British subjects (as they were just under the protection of the Crown). They were referred to as British Protected Persons.