SkPDF: skpdfdocument and skpdfpage use skpdfdevice in a const way

src/pdf/SkPDFDocument.h

Index: src/pdf/SkPDFDocument.h
diff --git a/src/pdf/SkPDFDocument.h b/src/pdf/SkPDFDocument.h
index e4c0521cbe0472bea31f0f783b1cbdbf0eee2568..c49e6397a1ea76c90cf0c194d0aecc875f2d3f64 100644
--- a/src/pdf/SkPDFDocument.h
+++ b/src/pdf/SkPDFDocument.h
@@ -11,17 +11,10 @@
 #define SkPDFDocument_DEFINED
 
 #include "SkAdvancedTypefaceMetrics.h"
-#include "SkRefCnt.h"
+#include "SkPDFDevice.h"
 #include "SkTDArray.h"
-#include "SkTemplates.h"
 
-class SkPDFCatalog;
-class SkPDFDevice;
-class SkPDFDict;
-class SkPDFPage;
-class SkPDFObject;
 class SkWStream;
-template <typename T> class SkTSet;
 
 /** \class SkPDFDocument
 
@@ -46,7 +39,7 @@ public:
      *
      *  @param pdfDevice The page to add to this document.
      */
-    bool appendPage(SkPDFDevice* pdfDevice) {
+    bool appendPage(const SkPDFDevice* pdfDevice) {
         fPageDevices.push(SkRef(pdfDevice));
         return true;
     }
@@ -59,7 +52,7 @@ public:
         int* notEmbedddableCount) const;
 
 private:
-    SkTDArray<SkPDFDevice*> fPageDevices;
+    SkTDArray<const SkPDFDevice*> fPageDevices;
 };
 
 #endif