Defer image surface destruction until next paint

Fixes #4043

(cherry picked from commit dbf786e456f2792476791caf9dadfeb43e9ab383)

common/gal/cairo/cairo_gal.cpp

@@ -83,6 +83,9 @@ CAIRO_GAL_BASE::~CAIRO_GAL_BASE()
 
     if( context )
         cairo_destroy( context );
+
+    for( auto imageSurface : imageSurfaces )
+        cairo_surface_destroy( imageSurface );
 }
 
 
@@ -508,7 +511,9 @@ void CAIRO_GAL_BASE::DrawBitmap( const BITMAP_BASE& aBitmap )
     cairo_surface_mark_dirty( image );
     cairo_set_source_surface( currentContext, image, 0, 0 );
     cairo_paint( currentContext );
-    cairo_surface_destroy( image );
+
+    // store the image handle so it can be destroyed later
+    imageSurfaces.push_back( image );
 
     isElementAdded = true;
 
@@ -929,6 +934,11 @@ void CAIRO_GAL_BASE::EnableDepthTest( bool aEnabled )
 
 void CAIRO_GAL_BASE::resetContext()
 {
+    for( auto imageSurface : imageSurfaces )
+        cairo_surface_destroy( imageSurface );
+
+    imageSurfaces.clear();
+
     ClearScreen();
 
     // Compute the world <-> screen transformations

include/gal/cairo/cairo_gal.h

@@ -304,6 +304,9 @@ protected:
     cairo_t*            context;                ///< Cairo image
     cairo_surface_t*    surface;                ///< Cairo surface
 
+    /// List of surfaces that were created by painting images, to be cleaned up later
+    std::vector<cairo_surface_t*> imageSurfaces;
+
     std::vector<cairo_matrix_t> xformStack;
 
     void flushPath();