[Sync] Convert sync to a static library.

components/sync/base/attachment_id_proto.h

Index: components/sync/base/attachment_id_proto.h
diff --git a/components/sync/base/attachment_id_proto.h b/components/sync/base/attachment_id_proto.h
index 2d8c54120bab3723707b9e309161c2978362f28d..fe41bb3ced8f7a41fdbb48c92e947d51d5ac1fd2 100644
--- a/components/sync/base/attachment_id_proto.h
+++ b/components/sync/base/attachment_id_proto.h
@@ -8,7 +8,6 @@
 #include <stddef.h>
 #include <stdint.h>
 
-#include "components/sync/base/sync_export.h"
 #include "components/sync/protocol/sync.pb.h"
 
 namespace syncer {
@@ -20,15 +19,15 @@ namespace syncer {
 // |size| is the size in bytes of the attachment identified by this proto.
 //
 // |crc32c| is the crc32c of the attachment identified by this proto.
-SYNC_EXPORT sync_pb::AttachmentIdProto CreateAttachmentIdProto(size_t size,
-                                                               uint32_t crc32c);
+sync_pb::AttachmentIdProto CreateAttachmentIdProto(size_t size,
+                                                   uint32_t crc32c);
 
 // Creates an AttachmentMetadata object from a repeated field of
 // AttachmentIdProto objects.
 //
 // Note: each record in the AttachmentMetadata will be marked as "on the
 // server".
-SYNC_EXPORT sync_pb::AttachmentMetadata CreateAttachmentMetadata(
+sync_pb::AttachmentMetadata CreateAttachmentMetadata(
     const google::protobuf::RepeatedPtrField<sync_pb::AttachmentIdProto>& ids);
 
 }  // namespace syncer