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/libmediaextractor/MediaBufferGroup.cpp b/media/libmediaextractor/MediaBufferGroup.cpp
index 22f01a5..2a8dd41 100644
--- a/media/libmediaextractor/MediaBufferGroup.cpp
+++ b/media/libmediaextractor/MediaBufferGroup.cpp
@@ -40,7 +40,7 @@
     Mutex mLock;
     Condition mCondition;
     size_t mGrowthLimit;  // Do not automatically grow group larger than this.
-    std::list<MediaBuffer *> mBuffers;
+    std::list<MediaBufferBase *> mBuffers;
 };
 
 MediaBufferGroup::MediaBufferGroup(size_t growthLimit)
@@ -94,7 +94,7 @@
 }
 
 MediaBufferGroup::~MediaBufferGroup() {
-    for (MediaBuffer *buffer : mInternal->mBuffers) {
+    for (MediaBufferBase *buffer : mInternal->mBuffers) {
         if (buffer->refcount() != 0) {
             const int localRefcount = buffer->localRefcount();
             const int remoteRefcount = buffer->remoteRefcount();
@@ -119,7 +119,7 @@
     delete mInternal;
 }
 
-void MediaBufferGroup::add_buffer(MediaBuffer *buffer) {
+void MediaBufferGroup::add_buffer(MediaBufferBase *buffer) {
     Mutex::Autolock autoLock(mInternal->mLock);
 
     // if we're above our growth limit, release buffers if we can
@@ -144,7 +144,7 @@
     if (mInternal->mBuffers.size() < mInternal->mGrowthLimit) {
         return true; // We can add more buffers internally.
     }
-    for (MediaBuffer *buffer : mInternal->mBuffers) {
+    for (MediaBufferBase *buffer : mInternal->mBuffers) {
         if (buffer->refcount() == 0) {
             return true;
         }
@@ -153,11 +153,11 @@
 }
 
 status_t MediaBufferGroup::acquire_buffer(
-        MediaBuffer **out, bool nonBlocking, size_t requestedSize) {
+        MediaBufferBase **out, bool nonBlocking, size_t requestedSize) {
     Mutex::Autolock autoLock(mInternal->mLock);
     for (;;) {
         size_t smallest = requestedSize;
-        MediaBuffer *buffer = nullptr;
+        MediaBufferBase *buffer = nullptr;
         auto free = mInternal->mBuffers.end();
         for (auto it = mInternal->mBuffers.begin(); it != mInternal->mBuffers.end(); ++it) {
             if ((*it)->refcount() == 0) {
@@ -217,7 +217,7 @@
     return mInternal->mBuffers.size();
 }
 
-void MediaBufferGroup::signalBufferReturned(MediaBuffer *) {
+void MediaBufferGroup::signalBufferReturned(MediaBufferBase *) {
     Mutex::Autolock autoLock(mInternal->mLock);
     mInternal->mCondition.signal();
 }