Add aliases to chromium nullity annotations

[johnkrah]

[Problem]
Chromium has implemented copies/extensions of Nullaway annotations which is not
yet recognized by Checker Framework.
See also: https://chromium-review.googlesource.com/c/chromium/src/+/6065417

[Solution]
This change adds aliases of chromium's new non-null and nullable
annotations to Checker Framework.

[Testing]
Building java classes in a derivative module using chromium APIs
correctly exits with no warning when passing a null value to a method
parameter annotated org.chromium.build.annotations.Nullable.

For example, these warnings were emitted after chromium added new
annotation https://source.chromium.org/chromium/chromium/src/+/main:ui/android/java/src/org/chromium/ui/display/DisplayAndroid.java;l=325-326

import org.chromium.build.annotations.Nullable;
...
            @Nullable Float xdpi,
            @Nullable Float ydpi,

and are no longer emitted after this pull request applied to checker.

XyzActivity.java:0: warning: [argument] incompatible argument for parameter xdpi of DisplayAndroid.update.
                null, // Float xdpi
                ^
  found   : null (NullType)
  required: @Initialized @NonNull Float
XyzActivity.java:0: warning: [argument] incompatible argument for parameter ydpi of DisplayAndroid.update.
                null, // Float ydpi
                ^
  found   : null (NullType)
  required: @Initialized @NonNull Float

Added clean-room local re-implementation of the classes, following
recent example given by mernst in 3d01348

[mernst]

Thanks!

I have two comments:

• It would be nice to include all of the org.chromium annotations in one pull request, so that we don't overlook any of them.

• It looks to me like one of the annotations already in this pull request is being aliased incorrectly, unless I am mistaken.

[johnkrah]

the main chromium nullness annotations mapped to checker aliases:

• Nullable : synonymous
• OptimizeAsNonNull --> NonNull
• EnsuresNonNull : synonymous
• EnsuresNonNullIf : synonymous
• RequiresNonNull : synonymous

some additional chromium annotations that may be of interest to nullness checker. I noticed checker has an alias list for PolyNull as well but I don't think any of these align to that proof. and I didn't find an equivalent for one of my favorite proofs MonotonicNonNull either.

• Contract : returns false if null, true if non-null i.e. evaluates param != null
• NullMarked : means this class is in scope for nullness checker
• NullUnmarked : means this class is out of scope for nullness checker

the remaining new chromium annotations are probably not nullness related:

• AlwaysInline
• CheckDiscard
• DoNotClassMerge
• DoNotInline
• DoNotStripLogs
• IdentifierNameString
• Initializer
• MockedInTests
• ServiceImpl
• UsedByReflection
• UsedReflectively

[johnkrah]

I see there are some tests failing now, taking a look and will update.

I had tried adding aliases for chromium's versions of EnsuresNonNull, EnsuresNonNullIf, RequiresNonNull along with copying their elements, but that seemed to break the purity of checker's EnsuresNonNull annotation itself, so I backed that out for now at least.

[johnkrah]

hi @mernst checking in for any further comments or questions, thanks for taking a look at this pull req, cheers!

[johnkrah]

updating pr with rebase on the the recent commit 618b9a0