Add total size of DMA-BUFs exported to 'dumpsys meminfo'

When ION support is not detected, print the total size of DMA-BUFs
exported as part of dumpsys meminfo.

Bug: 167709539
Test: dumpsys meminfo
Change-Id: I3439a8f00cf1aef37e5043b505ed53d47a8a4756
Merged-In: I3439a8f00cf1aef37e5043b505ed53d47a8a4756

core/java/android/os/Debug.java

@@ -2550,6 +2550,14 @@ public final class Debug
      */
     public static native long getZramFreeKb();
 
+    /**
+     * Return total memory size in kilobytes for exported DMA-BUFs or -1 if
+     * the DMA-BUF sysfs stats at /sys/kernel/dmabuf/buffers could not be read.
+     *
+     * @hide
+     */
+    public static native long getDmabufTotalExportedKb();
+
     /**
      * Return memory size in kilobytes allocated for ION heaps or -1 if
      * /sys/kernel/ion/total_heaps_kb could not be read.