Add observer for BAAnnots from Javascript

fpdfsdk/javascript/Annot.h

Index: fpdfsdk/javascript/Annot.h
diff --git a/fpdfsdk/javascript/Annot.h b/fpdfsdk/javascript/Annot.h
index b3ea292aed86e3a30e6912058477e3bed590b31c..be850350aea4cf6c02e84e5ee93a4e564737051c 100644
--- a/fpdfsdk/javascript/Annot.h
+++ b/fpdfsdk/javascript/Annot.h
@@ -7,6 +7,8 @@
 #ifndef FPDFSDK_JAVASCRIPT_ANNOT_H_
 #define FPDFSDK_JAVASCRIPT_ANNOT_H_
 
+#include <memory>
+
 #include "fpdfsdk/include/cpdfsdk_baannot.h"
 #include "fpdfsdk/javascript/JS_Define.h"
 
@@ -22,7 +24,8 @@ class Annot : public CJS_EmbedObj {
   void SetSDKAnnot(CPDFSDK_BAAnnot* annot);
 
  private:
-  CPDFSDK_BAAnnot* m_BAAnnot = nullptr;
+  CPDFSDK_Annot* m_pAnnot = nullptr;
+  std::unique_ptr<CPDFSDK_Annot::Observer> m_pObserver;

[Tom Sepez, 2016/09/06 20:27:05]

Maybe it should inherit from this rather than having one, eg. the object itself
can observe destruction.  Is that the usual pattern? Does that imply that
Observer is a virtual API?

[dsinclair, 2016/09/06 20:32:20]

We would need to change Observer in that case, currently it accepts the thing to
observe in the constructor, but in this case we don't know the annotation until
SetSDKAnnot is called.

I can make that change, to allow a nullptr as the observed object and provide a
setter, but is that complexity we want in the observer?

I guess my question becomes, is it strange that Annot is-a
CPDFSDK_Annot::Observer but has-a CPDFSDK_Annot?

Feels like the observer is making Annot into a different level of object by
pulling it into CPDFSDK_Annot world?

 };
 
 class CJS_Annot : public CJS_Object {