need to call SetFrameSize on Resize

otherwise if the crop tab is not the initial tab shown then
it doesn't repaint correctly when it is shown

Change-Id: Ie61819fe3fb089b716547fa5e54352ae04fd8087

cui/source/inc/grfpage.hxx

@@ -36,6 +36,7 @@ public:
     SvxCropExample( Window* pPar, WinBits nStyle );
 
     virtual void Paint( const Rectangle& rRect );
+    virtual void Resize();
     virtual Size GetOptimalSize() const;
 
     void SetTopLeft( const Point& rNew )    { aTopLeft = rNew; }

cui/source/tabpages/grfpage.cxx

@@ -786,6 +786,11 @@ void SvxCropExample::Paint( const Rectangle& )
     DrawRect( aRect );
 }
 
+void SvxCropExample::Resize()
+{
+    SetFrameSize(aFrameSize);
+}
+
 void SvxCropExample::SetFrameSize( const Size& rSz )
 {
     aFrameSize = rSz;