BufferQueue: track buffer-queue by instance vs. by reference

Instead of representing the buffer-queue as a vector of buffer
indices, represent them as a vector of BufferItems (copies).
This allows modifying the buffer slots independent of the queued
buffers.

As part of this change, BufferSlot properties that are only
been relevant in the buffer-queue have been removed.

Also, invalid scalingMode in queueBuffer now returns an error.

ConsumerBase has also changed to allow reuse of the same
buffer slots by different buffers.

Change-Id: If2a698fa142b67c69ad41b8eaca6e127eb3ef75b
Signed-off-by: Lajos Molnar <lajos@google.com>
Related-to-bug: 7093648
diff --git a/libs/gui/CpuConsumer.cpp b/libs/gui/CpuConsumer.cpp
index 0543649..0834361 100644
--- a/libs/gui/CpuConsumer.cpp
+++ b/libs/gui/CpuConsumer.cpp
@@ -189,7 +189,9 @@
     // disconnected after this buffer was acquired.
     if (CC_LIKELY(mAcquiredBuffers[lockedIdx].mGraphicBuffer ==
             mSlots[buf].mGraphicBuffer)) {
-        releaseBufferLocked(buf, EGL_NO_DISPLAY, EGL_NO_SYNC_KHR);
+        releaseBufferLocked(
+                buf, mAcquiredBuffers[lockedIdx].mGraphicBuffer,
+                EGL_NO_DISPLAY, EGL_NO_SYNC_KHR);
     }
 
     AcquiredBuffer &ab = mAcquiredBuffers.editItemAt(lockedIdx);