Merge changes Ibe310d58,If88dceda into main

* changes:
  Move Cow Header child writer
  Add v3 Cow Header
diff --git a/fs_mgr/libsnapshot/include/libsnapshot/cow_format.h b/fs_mgr/libsnapshot/include/libsnapshot/cow_format.h
index bfa8f6b..b271dad 100644
--- a/fs_mgr/libsnapshot/include/libsnapshot/cow_format.h
+++ b/fs_mgr/libsnapshot/include/libsnapshot/cow_format.h
@@ -91,6 +91,18 @@
 
     // Scratch space used during merge
     uint32_t buffer_size;
+
+} __attribute__((packed));
+
+struct CowHeaderV3 : public CowHeader {
+    // Location of sequence buffer in COW.
+    uint64_t sequence_buffer_offset;
+    // Size, in bytes, of the CowResumePoint buffer.
+    uint32_t resume_buffer_size;
+    // Size, in bytes, of the CowOperation buffer.
+    uint32_t op_buffer_size;
+    // Compression Algorithm
+    uint32_t compression_algorithm;
 } __attribute__((packed));
 
 // This structure is the same size of a normal Operation, but is repurposed for the footer.
diff --git a/fs_mgr/libsnapshot/libsnapshot_cow/writer_base.h b/fs_mgr/libsnapshot/libsnapshot_cow/writer_base.h
index cdf6222..709b248 100644
--- a/fs_mgr/libsnapshot/libsnapshot_cow/writer_base.h
+++ b/fs_mgr/libsnapshot/libsnapshot_cow/writer_base.h
@@ -63,7 +63,6 @@
     bool ValidateNewBlock(uint64_t new_block);
 
     CowOptions options_;
-    CowHeader header_{};
 
     android::base::unique_fd fd_;
     bool is_dev_null_ = false;
diff --git a/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.cpp b/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.cpp
index e51dbde..a6f449f 100644
--- a/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.cpp
+++ b/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.cpp
@@ -243,7 +243,7 @@
 
     // Headers are not complete, but this ensures the file is at the right
     // position.
-    if (!android::base::WriteFully(fd_, &header_, sizeof(header_))) {
+    if (!android::base::WriteFully(fd_, &header_, sizeof(CowHeader))) {
         PLOG(ERROR) << "write failed";
         return false;
     }
@@ -262,7 +262,7 @@
         return false;
     }
 
-    if (lseek(fd_.get(), sizeof(header_) + header_.buffer_size, SEEK_SET) < 0) {
+    if (lseek(fd_.get(), sizeof(CowHeader) + header_.buffer_size, SEEK_SET) < 0) {
         PLOG(ERROR) << "lseek failed";
         return false;
     }
diff --git a/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.h b/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.h
index ce97b01..24170eb 100644
--- a/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.h
+++ b/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.h
@@ -63,6 +63,7 @@
 
   private:
     CowFooter footer_{};
+    CowHeader header_{};
     CowCompression compression_;
     // in the case that we are using one thread for compression, we can store and re-use the same
     // compressor