blast: cache buffers

Cache incoming buffers so they don't have to be imported by mapper
everytime they are set.

Amended by Change-Id: I3040f6d8886ca9b130115784c199edfdd9c85c7e

Test: Transaction_test
Bug: 80477568
Change-Id: Icd167c5e5bd59d7331b829667b1139919393d98b
diff --git a/libs/gui/LayerState.cpp b/libs/gui/LayerState.cpp
index e5170ab..40b55fa 100644
--- a/libs/gui/LayerState.cpp
+++ b/libs/gui/LayerState.cpp
@@ -94,6 +94,9 @@
         }
     }
 
+    output.writeStrongBinder(cachedBuffer.token);
+    output.writeInt32(cachedBuffer.bufferId);
+
     return NO_ERROR;
 }
 
@@ -164,6 +167,9 @@
         listenerCallbacks.emplace_back(listener, callbackIds);
     }
 
+    cachedBuffer.token = input.readStrongBinder();
+    cachedBuffer.bufferId = input.readInt32();
+
     return NO_ERROR;
 }
 
@@ -372,6 +378,10 @@
     }
 #endif
 
+    if (other.what & eCachedBufferChanged) {
+        what |= eCachedBufferChanged;
+        cachedBuffer = other.cachedBuffer;
+    }
     if ((other.what & what) != other.what) {
         ALOGE("Unmerged SurfaceComposer Transaction properties. LayerState::merge needs updating? "
               "other.what=0x%" PRIu64 " what=0x%" PRIu64,