Copy more @CanIgnoreReturnValue annotations to GWT emulations.

RELNOTES=n/a
PiperOrigin-RevId: 461928636

Author: cpovirk

guava-gwt/src-super/com/google/common/collect/super/com/google/common/collect/MapMaker.java

@@ -18,6 +18,7 @@
 
 import static com.google.common.base.Preconditions.checkArgument;
 
+import com.google.errorprone.annotations.CanIgnoreReturnValue;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
 
@@ -31,6 +32,7 @@ public final class MapMaker {
 
   public MapMaker() {}
 
+  @CanIgnoreReturnValue
   public MapMaker initialCapacity(int initialCapacity) {
     if (initialCapacity < 0) {
       throw new IllegalArgumentException();
@@ -39,6 +41,7 @@ public MapMaker initialCapacity(int initialCapacity) {
     return this;
   }
 
+  @CanIgnoreReturnValue
   public MapMaker concurrencyLevel(int concurrencyLevel) {
     checkArgument(
         concurrencyLevel >= 1, "concurrency level (%s) must be at least 1", concurrencyLevel);

guava-gwt/src-super/com/google/common/util/concurrent/super/com/google/common/util/concurrent/AbstractFuture.java

@@ -51,11 +51,13 @@ public abstract class AbstractFuture<V> extends InternalFutureFailureAccess
   interface Trusted<V> extends ListenableFuture<V> {}
 
   abstract static class TrustedFuture<V> extends AbstractFuture<V> implements Trusted<V> {
+    @CanIgnoreReturnValue
     @Override
     public final V get() throws InterruptedException, ExecutionException {
       return super.get();
     }
 
+    @CanIgnoreReturnValue
     @Override
     public final V get(long timeout, TimeUnit unit)
         throws InterruptedException, ExecutionException, TimeoutException {
@@ -132,12 +134,14 @@ public boolean isDone() {
   /*
    * ForwardingFluentFuture needs to override those methods, so they are not final.
    */
+  @CanIgnoreReturnValue
   @Override
   public V get() throws InterruptedException, ExecutionException {
     state.maybeThrowOnGet(throwable);
     return value;
   }
 
+  @CanIgnoreReturnValue
   @Override
   public V get(long timeout, TimeUnit unit)
       throws InterruptedException, ExecutionException, TimeoutException {