Any should not unsubscribe downstream.
Fixed OperatorAll unsubscribing downstream.
Fixed first emission racing with pre and post subscription.
Add "Subscriptions.unsubscribed" to fix the 'isUnsubscribed' issue
Remove extraneous request(n) and onCompleted() calls when unsubscribed.
Remove ActionSubscription
Fixed timer cast-to-int crash causing incorrect benchmark.
Fix 'request(0)' issue in Scan
Merge pull request #1947 from akarnokd/ReplaySubjectFirstEmissionFix

Fixed first emission racing with pre and post subscription.
Merge pull request #1951 from abersnaze/unnecessary

Remove extraneous request(n) and onCompleted() calls when unsubscribed.
Merge pull request #1952 from zsxwing/remove-action-subscription

Remove ActionSubscription
Merge pull request #1953 from akarnokd/OperatorSerializePerfFix

Fixed timer cast-to-int crash causing incorrect benchmark.
doOnRequest

Similar to doOnSubscribe, doOnNext, etc
SerialSubscription and MultipleAssignmentSubscription should use Subscriptions.empty()
Merge pull request #1960 from benjchristensen/doOnRequest

doOnRequest
Remove Request Batching in Merge

Removing the batching until we can find a correct way to do it.

The performance impact of this change is seen here:

Benchmark                                          (size)   Mode   Samples          1.x    No Request Batching
r.o.OperatorMergePerf.merge1SyncStreamOfN               1  thrpt         5  4585554.607    4666745.314 102%
r.o.OperatorMergePerf.merge1SyncStreamOfN            1000  thrpt         5    51273.033      39922.246 78%
r.o.OperatorMergePerf.merge1SyncStreamOfN         1000000  thrpt         5       47.515         37.634 79%
r.o.OperatorMergePerf.mergeNAsyncStreamsOfN             1  thrpt         5    90901.735      93454.726 103%
r.o.OperatorMergePerf.mergeNAsyncStreamsOfN          1000  thrpt         5        5.407          4.910 91%
r.o.OperatorMergePerf.mergeNSyncStreamsOf1              1  thrpt         5  4181618.767    4173322.551 100%
r.o.OperatorMergePerf.mergeNSyncStreamsOf1            100  thrpt         5   422193.599     408972.130 97%
r.o.OperatorMergePerf.mergeNSyncStreamsOf1           1000  thrpt         5    36886.812      36448.978 99%
r.o.OperatorMergePerf.mergeNSyncStreamsOfN              1  thrpt         5  4815945.720    4887943.643 101%
r.o.OperatorMergePerf.mergeNSyncStreamsOfN           1000  thrpt         5       43.926         39.027 89%
r.o.OperatorMergePerf.mergeTwoAsyncStreamsOfN           1  thrpt         5    72578.046      70412.656 97%
r.o.OperatorMergePerf.mergeTwoAsyncStreamsOfN        1000  thrpt         5     3260.024       3064.403 94%
r.o.OperatorMergePerf.oneStreamOfNthatMergesIn1         1  thrpt         5  4678858.201    4808504.588 103%
r.o.OperatorMergePerf.oneStreamOfNthatMergesIn1      1000  thrpt         5    34407.547      36364.476 106%
r.o.OperatorMergePerf.oneStreamOfNthatMergesIn1   1000000  thrpt         5       31.312         32.261 103%
Handle 0 or negative request in Buffer
Fix NPE when the key is null in GroupBy
Fix the issue that Sample doesn't call 'unsubscribe'
add @since section to doOnRequest() javadocs