Reset buffer after stop protolog to file

After protolog-to-file stops, BaseProtoLogImpl.mBuffer still uses a lot of memory.

Bug: 262244460
Merged-In: If618dad902df3c7fc1b2a943fe550c7c34a2d65e
Change-Id: If618dad902df3c7fc1b2a943fe550c7c34a2d65e

core/java/com/android/internal/protolog/BaseProtoLogImpl.java

@@ -255,6 +255,7 @@ public class BaseProtoLogImpl {
             if (writeToFile) {
                 writeProtoLogToFileLocked();
                 logAndPrintln(pw, "Log written to " + mLogFile + ".");
+                mBuffer.resetBuffer();
             }
             if (mProtoLogEnabled) {
                 logAndPrintln(pw, "ERROR: logging was re-enabled while waiting for flush.");