Rename nextTransaction to syncTransaction

The variable nextTransaction is abigious and doesn't represent its
purpose. Rename to syncTransaction

Test: BLASTBufferQueueTest
Bug: 200285149
Change-Id: I1c1e151a63e88127178a92a369e82bcc6770ab90
diff --git a/libs/gui/include/gui/BLASTBufferQueue.h b/libs/gui/include/gui/BLASTBufferQueue.h
index 4a63544..f718de8 100644
--- a/libs/gui/include/gui/BLASTBufferQueue.h
+++ b/libs/gui/include/gui/BLASTBufferQueue.h
@@ -94,7 +94,7 @@
                                      const std::vector<SurfaceControlStats>& stats);
     void releaseBufferCallback(const ReleaseCallbackId& id, const sp<Fence>& releaseFence,
                                std::optional<uint32_t> currentMaxAcquiredBufferCount);
-    void setNextTransaction(SurfaceComposerClient::Transaction *t);
+    void setSyncTransaction(SurfaceComposerClient::Transaction* t);
     void mergeWithNextTransaction(SurfaceComposerClient::Transaction* t, uint64_t frameNumber);
     void applyPendingTransactions(uint64_t frameNumber);
 
@@ -208,7 +208,7 @@
     sp<IGraphicBufferProducer> mProducer;
     sp<BLASTBufferItemConsumer> mBufferItemConsumer;
 
-    SurfaceComposerClient::Transaction* mNextTransaction GUARDED_BY(mMutex);
+    SurfaceComposerClient::Transaction* mSyncTransaction GUARDED_BY(mMutex);
     std::vector<std::tuple<uint64_t /* framenumber */, SurfaceComposerClient::Transaction>>
             mPendingTransactions GUARDED_BY(mMutex);