Deal with ca and CA transparency operators in pdf. add comments to generated classes.

experimental/PdfViewer/SkPdfCheckboxFieldDictionary_autogen.h

 #ifndef __DEFINED__SkPdfCheckboxFieldDictionary
 #define __DEFINED__SkPdfCheckboxFieldDictionary
 
 #include "SkPdfEnums_autogen.h"
 #include "SkPdfArray_autogen.h"
 #include "SkPdfDictionary_autogen.h"
 
+// Additional entry specific to a checkbox field
 class SkPdfCheckboxFieldDictionary : public SkPdfDictionary {
 public:
   virtual SkPdfObjectType getType() const { return kCheckboxFieldDictionary_SkPdfObjectType;}
   virtual SkPdfObjectType getTypeEnd() const { return (SkPdfObjectType)(kCheckboxFieldDictionary_SkPdfObjectType + 1);}
 public:
   virtual SkPdfCheckboxFieldDictionary* asCheckboxFieldDictionary() {return this;}
   virtual const SkPdfCheckboxFieldDictionary* asCheckboxFieldDictionary() const {return this;}
 
 private:
   virtual SkPdfALinkAnnotationDictionary* asALinkAnnotationDictionary() {return NULL;}
@@ skipping 496 matching lines @@
 
 public:
 private:
 public:
   SkPdfCheckboxFieldDictionary(const PdfMemDocument* podofoDoc = NULL, const PdfObject* podofoObj = NULL) : SkPdfDictionary(podofoDoc, podofoObj) {}
 
   virtual bool valid() const {return true;}
 
   SkPdfCheckboxFieldDictionary& operator=(const SkPdfCheckboxFieldDictionary& from) {this->fPodofoDoc = from.fPodofoDoc; this->fPodofoObj = from.fPodofoObj; return *this;}
 
+/** (Optional; inheritable; PDF 1.4) A text string to be used in place of the V entry for the
+ *  value of the field.
+**/
+  bool has_Opt() const {
+    return (ObjectFromDictionary(fPodofoDoc, fPodofoObj->GetDictionary(), "Opt", "", NULL));
+  }
+
   std::string Opt() const {
     std::string ret;
     if (StringFromDictionary(fPodofoDoc, fPodofoObj->GetDictionary(), "Opt", "", &ret)) return ret;
     // TODO(edisonn): warn about missing required field, assert for known good pdfs
     return "";
   }
 
 };
 
 #endif  // __DEFINED__SkPdfCheckboxFieldDictionary