Move resetting the composite reader index to before the release as it…

… that fails then the operation hasn't completed correctly and the ownership of the buffer should remain with the caller.

netty/src/main/java/io/grpc/netty/NettyAdaptiveCumulator.java

@@ -204,11 +204,8 @@ static void mergeWithCompositeTail(
       composite.addFlattenedComponents(true, newTail);
       // New tail's ownership transferred to the composite buf.
       newTail = null;
-      in.release();
-      in = null;
-      // Restore the reader. In case it fails we restore the reader after releasing/forgetting
-      // the input and the new tail so that finally block can handles them properly.
       composite.readerIndex(prevReader);
+      in.release(); // Successful so took over ownership of in
     } finally {
       // If new tail's ownership isn't transferred to the composite buf.
       // Release it to prevent a leak.

netty/src/test/java/io/grpc/netty/NettyAdaptiveCumulatorTest.java

@@ -536,7 +536,7 @@ public CompositeByteBuf addFlattenedComponents(boolean increaseWriterIndex,
         fail("Cumulator didn't throw");
       } catch (UnsupportedOperationException actualError) {
         assertSame(expectedError, actualError);
-        // Input must be released unless its ownership has been to the composite cumulation.
+        // Because of error, ownership shouldn't have changed so should not have been released.
         assertEquals(1, in.refCnt());
         // Tail released
         assertEquals(0, tail.refCnt());
@@ -573,7 +573,7 @@ public CompositeByteBuf addFlattenedComponents(boolean increaseWriterIndex,
         fail("Cumulator didn't throw");
       } catch (UnsupportedOperationException actualError) {
         assertSame(expectedError, actualError);
-        // Input must be released unless its ownership has been to the composite cumulation.
+        // Because of error, ownership shouldn't have changed so should not have been released.
         assertEquals(1, in.refCnt());
         // New buffer released
         assertEquals(0, newTail.refCnt());