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/include/gui/GLConsumer.h b/include/gui/GLConsumer.h
index 1e88927..031684e 100644
--- a/include/gui/GLConsumer.h
+++ b/include/gui/GLConsumer.h
@@ -241,11 +241,13 @@
 
     // releaseBufferLocked overrides the ConsumerBase method to update the
     // mEglSlots array in addition to the ConsumerBase.
-    virtual status_t releaseBufferLocked(int buf, EGLDisplay display,
-           EGLSyncKHR eglFence);
+    virtual status_t releaseBufferLocked(int slot,
+            const sp<GraphicBuffer> graphicBuffer,
+            EGLDisplay display, EGLSyncKHR eglFence);
 
-    status_t releaseBufferLocked(int buf, EGLSyncKHR eglFence) {
-        return releaseBufferLocked(buf, mEglDisplay, eglFence);
+    status_t releaseBufferLocked(int slot,
+            const sp<GraphicBuffer> graphicBuffer, EGLSyncKHR eglFence) {
+        return releaseBufferLocked(slot, graphicBuffer, mEglDisplay, eglFence);
     }
 
     static bool isExternalFormat(uint32_t format);