[SPARK-25114][2.3][CORE][FOLLOWUP] Fix RecordBinaryComparatorSuite build failure

## What changes were proposed in this pull request?

Fix RecordBinaryComparatorSuite build failure

## How was this patch tested?

Existing tests.

Closes #22166 from jiangxb1987/SPARK-25114-2.3.

Authored-by: Xingbo Jiang <xingbo.jiang@databricks.com>
Signed-off-by: Xiao Li <gatorsmile@gmail.com>

Author: jiangxb1987

core/src/test/java/org/apache/spark/memory/TestMemoryConsumer.java

@@ -19,6 +19,8 @@
 
 import java.io.IOException;
 
+import org.apache.spark.unsafe.memory.MemoryBlock;
+
 public class TestMemoryConsumer extends MemoryConsumer {
   public TestMemoryConsumer(TaskMemoryManager memoryManager, MemoryMode mode) {
     super(memoryManager, 1024L, mode);
@@ -43,6 +45,11 @@ void free(long size) {
     used -= size;
     taskMemoryManager.releaseExecutionMemory(size, this);
   }
+
+  public void freePage(MemoryBlock page) {
+    used -= page.size();
+    taskMemoryManager.freePage(page, this);
+  }
 }