Add MediaBufferBase and use it in MediaSource and MediaBufferGroup.

MediaBuffer class exposes internal classes, ABuffer and IMemory, which
we don't want to expose to plugins. This change introduces
MediaBufferBase which does not expose any classes from system library.

Test: build and post-submit media cts tests
Bug: 67908556
Change-Id: Ic9ee239caf9b84b2b3740e2d533257afa25c8784
diff --git a/media/libmedia/IMediaSource.cpp b/media/libmedia/IMediaSource.cpp
index 0d5127c..f6b9255 100644
--- a/media/libmedia/IMediaSource.cpp
+++ b/media/libmedia/IMediaSource.cpp
@@ -113,9 +113,9 @@
         return NULL;
     }
 
-    virtual status_t read(MediaBuffer **buffer,
+    virtual status_t read(MediaBufferBase **buffer,
             const MediaSource::ReadOptions *options) {
-        Vector<MediaBuffer *> buffers;
+        Vector<MediaBufferBase *> buffers;
         status_t ret = readMultiple(&buffers, 1 /* maxNumBuffers */, options);
         *buffer = buffers.size() == 0 ? nullptr : buffers[0];
         ALOGV("read status %d, bufferCount %u, sinceStop %u",
@@ -124,7 +124,7 @@
     }
 
     virtual status_t readMultiple(
-            Vector<MediaBuffer *> *buffers, uint32_t maxNumBuffers,
+            Vector<MediaBufferBase *> *buffers, uint32_t maxNumBuffers,
             const MediaSource::ReadOptions *options) {
         ALOGV("readMultiple");
         if (buffers == NULL || !buffers->isEmpty()) {
@@ -341,7 +341,7 @@
             uint32_t bufferCount = 0;
             for (; bufferCount < maxNumBuffers; ++bufferCount, ++mBuffersSinceStop) {
                 MediaBuffer *buf = nullptr;
-                ret = read(&buf, useOptions ? &opts : nullptr);
+                ret = read((MediaBufferBase **)&buf, useOptions ? &opts : nullptr);
                 opts.clearNonPersistent(); // Remove options that only apply to first buffer.
                 if (ret != NO_ERROR || buf == nullptr) {
                     break;
@@ -364,7 +364,7 @@
                     } else {
                         ALOGD("Large buffer %zu without IMemory!", length);
                         ret = mGroup->acquire_buffer(
-                                &transferBuf, false /* nonBlocking */, length);
+                                (MediaBufferBase **)&transferBuf, false /* nonBlocking */, length);
                         if (ret != OK
                                 || transferBuf == nullptr
                                 || transferBuf->mMemory == nullptr) {