Enable test-stressgraphics-firefox-skip3d

Try to run stressGraphics with firefox, but without 3d

On several platforms (like Windows and sometime Mac) firefox
has problem to initialize WebGL and fallback solution does not work
properly

test/CMakeLists.txt

@@ -183,14 +183,14 @@ if(ROOT_opengl_FOUND)
                   FAILREGEX "FAILED|Error in"
                   LABELS longtest)
   endif()
-  # if(FIREFOX_EXECUTABLE AND NOT APPLE AND NOT MSVC)
-  #    ROOT_ADD_TEST(test-stressgraphics-firefox
-  #                  RUN_SERIAL
-  #                  ENVIRONMENT LD_LIBRARY_PATH=${CMAKE_BINARY_DIR}/lib:$ENV{LD_LIBRARY_PATH}
-  #                  COMMAND stressGraphics -b -k -p=sgf --web=firefox
-  #                  FAILREGEX "FAILED|Error in"
-  #                  LABELS longtest)
-  # endif()
+  if(FIREFOX_EXECUTABLE)
+    ROOT_ADD_TEST(test-stressgraphics-firefox-skip3d
+                  RUN_SERIAL
+                  ENVIRONMENT LD_LIBRARY_PATH=${CMAKE_BINARY_DIR}/lib:$ENV{LD_LIBRARY_PATH}
+                  COMMAND stressGraphics -b -k -p=sgf --web=firefox -skip3d
+                  FAILREGEX "FAILED|Error in"
+                  LABELS longtest)
+  endif()
 endif()
 
 #--stressHistogram------------------------------------------------------------------------------------