[sync] Componentize sync: Part 6: Add more SYNC_EXPORTs to files in src/sync/

sync/internal_api/public/base/invalidation.h

Index: sync/internal_api/public/base/invalidation.h
diff --git a/sync/internal_api/public/base/invalidation.h b/sync/internal_api/public/base/invalidation.h
index 18afcabdd747203d72d913869726e478fb51aee9..ec11309d33ef3081ce715018bba36cc60eca0ac5 100644
--- a/sync/internal_api/public/base/invalidation.h
+++ b/sync/internal_api/public/base/invalidation.h
@@ -32,6 +32,8 @@ class SYNC_EXPORT AckHandle {
 
   bool IsValid() const;
 
+  virtual ~AckHandle();
+
  private:
   // Explicitly copyable and assignable for STL containers.
   AckHandle(const std::string& state, base::Time timestamp);
@@ -45,8 +47,9 @@ class SYNC_EXPORT AckHandle {
 // associated ack handle that an InvalidationHandler implementation can use to
 // acknowledge receipt of the invalidation. It does not embed the object ID,
 // since it is typically associated with it through ObjectIdInvalidationMap.
-struct Invalidation {
+struct SYNC_EXPORT Invalidation {
   Invalidation();
+  virtual ~Invalidation();
 
   bool Equals(const Invalidation& other) const;