Add explanatory comments

Author: jack-berg

sdk/metrics/src/main/java/io/opentelemetry/sdk/metrics/internal/aggregator/DoubleBase2ExponentialHistogramAggregator.java

@@ -267,6 +267,9 @@ protected boolean isDoubleType() {
 
     @Override
     public void recordLong(long value, Attributes attributes, Context context) {
+      // Since there is no LongExplicitBucketHistogramAggregator and we need to support measurements
+      // from LongHistogram, we redirect calls from #recordLong to #recordDouble. Without this, the
+      // base AggregatorHandle implementation of #recordLong throws.
       super.recordDouble((double) value, attributes, context);
     }
 

sdk/metrics/src/main/java/io/opentelemetry/sdk/metrics/internal/aggregator/DoubleExplicitBucketHistogramAggregator.java

@@ -132,6 +132,9 @@ static final class Handle extends AggregatorHandle<HistogramPointData> {
 
     @Override
     public void recordLong(long value, Attributes attributes, Context context) {
+      // Since there is no LongExplicitBucketHistogramAggregator and we need to support measurements
+      // from LongHistogram, we redirect calls from #recordLong to #recordDouble. Without this, the
+      // base AggregatorHandle implementation of #recordLong throws.
       super.recordDouble((double) value, attributes, context);
     }