let SwTextBoxHelper::findTextBoxes() take a const SwDoc

Change-Id: Icb1540b93f4117999b755d4d5fd387f1228250aa

sw/inc/textboxhelper.hxx

@@ -41,7 +41,7 @@ public:
     static SwFrmFmt* findTextBox(SwFrmFmt* pShape);
 
     /// Look up TextFrames in a document, which are in fact TextBoxes.
-    static std::list<SwFrmFmt*> findTextBoxes(SwDoc* pDoc);
+    static std::list<SwFrmFmt*> findTextBoxes(const SwDoc* pDoc);
     /// Count number of shapes in the document, excluding TextBoxes.
     static sal_Int32 getCount(SdrPage* pPage, std::list<SwFrmFmt*>& rTextBoxes);
     /// Get a shape by index, excluding TextBoxes.

sw/source/core/doc/textboxhelper.cxx

@@ -83,12 +83,12 @@ void SwTextBoxHelper::destroy(SwFrmFmt* pShape)
     }
 }
 
-std::list<SwFrmFmt*> SwTextBoxHelper::findTextBoxes(SwDoc* pDoc)
+std::list<SwFrmFmt*> SwTextBoxHelper::findTextBoxes(const SwDoc* pDoc)
 {
     std::list<SwFrmFmt*> aRet;
 
-    SwFrmFmts& rSpzFrmFmts = *pDoc->GetSpzFrmFmts();
-    for (SwFrmFmts::iterator it = rSpzFrmFmts.begin(); it != rSpzFrmFmts.end(); ++it)
+    const SwFrmFmts& rSpzFrmFmts = *pDoc->GetSpzFrmFmts();
+    for (SwFrmFmts::const_iterator it = rSpzFrmFmts.begin(); it != rSpzFrmFmts.end(); ++it)
     {
         SwFrmFmt* pTextBox = findTextBox(*it);
         if (pTextBox)