ignore ctx.restore() if in the initial state

calling cairo_restore on the initial state makes all drawing operations
afterwards do nothing, which does not match browser behavior

Author: chearon

src/CanvasRenderingContext2d.cc

@@ -233,8 +233,10 @@ Context2d::save() {
 
 void
 Context2d::restore() {
-  cairo_restore(_context);
-  restoreState();
+  if (stateno > 0) {
+    cairo_restore(_context);
+    restoreState();
+  }
 }
 
 /*
@@ -258,7 +260,6 @@ Context2d::saveState() {
 
 void
 Context2d::restoreState() {
-  if (0 == stateno) return;
   // Olaf (2011-02-21): Free old state data
 #if HAVE_PANGO
   free(states[stateno]->fontFamily);