Add missing @NonNull to BaseRecordingCanvas

Some improvements in Metalava's revealed an issue with missing
`@NonNull` annotations on 2 parameters of the `BaseRecordingCanvas`'s
`drawDoubleRoundRect()` method. They are present on the overridden
method but not on the overriding method. This change adds the
missing annotations.

Bug: 307926200
Test: m out/soong/.intermediates/frameworks/base/api/api-stubs-docs-non-updatable/android_common/metalava/api-stubs-docs-non-updatable-stubs.srcjar
Change-Id: I090c3f749e6ac2321d59189f5ec1a4f27179dd82