enable browser.test_sdl_ttf_render_text_solid on CircleCI

ttf-mscorefonts-installer allows for easy installation of the Microsoft
True Type Core Fonts for the Web including Arial. The package requires
acceptance of an EULA*. Informally speaking:

  These fonts were provided by Microsoft "in the interest of
  cross-platform compatibility". This is no longer the case, but they
  are still available from third parties.

  You are free to download these fonts and use them for your own use,
  but you may not redistribute them in modified form, including changes
  to the file name or packaging format.

* http://corefonts.sourceforge.net/eula.htm

Author: hujiajie

.circleci/config.yml

@@ -20,6 +20,7 @@ test-defaults: &test-defaults
         apt-get update
         # preseed packages so that apt-get won't prompt for user input
         echo "keyboard-configuration keyboard-configuration/layoutcode string us" | debconf-set-selections
+        echo "ttf-mscorefonts-installer msttcorefonts/accepted-mscorefonts-eula select true" | debconf-set-selections
         apt-get install -y python3 cmake build-essential openjdk-9-jre-headless $TEST_DEPENDENCY
         if [ x"$DISPLAY" != x ]; then
           # Start an X session. Openbox might be optional for now, but
@@ -140,7 +141,6 @@ jobs:
   test-browser:
     <<: *test-defaults
     environment:
-      # browser.test_sdl_ttf_render_text_solid depends on Arial from Microsoft
       # browser.test_sdl2_mouse and/or SDL2 should be fixed. The case happens
       # to be failing here, and the root cause might be related with the
       # initial position of the mouse pointer relative to the canvas.
@@ -150,9 +150,9 @@ jobs:
       # browser.test_webgl_offscreen_canvas_in_mainthread_after_pthread
       # are crashing Firefox (bugzil.la/1281796). The former case is
       # further blocked by issue #6897.
-      - TEST_TARGET=browser skip:browser.test_sdl_ttf_render_text_solid skip:browser.test_sdl2_mouse skip:browser.test_html5_webgl_create_context skip:browser.test_webgl_offscreen_canvas_in_pthread skip:browser.test_webgl_offscreen_canvas_in_mainthread_after_pthread
+      - TEST_TARGET=browser skip:browser.test_sdl2_mouse skip:browser.test_html5_webgl_create_context skip:browser.test_webgl_offscreen_canvas_in_pthread skip:browser.test_webgl_offscreen_canvas_in_mainthread_after_pthread
       # TODO: use Firefox headless mode when https://bugzil.la/1375585 resolves
-      - TEST_DEPENDENCY=dbus-x11 firefox menu openbox xinit xserver-xorg xserver-xorg-video-dummy
+      - TEST_DEPENDENCY=dbus-x11 firefox menu openbox ttf-mscorefonts-installer xinit xserver-xorg xserver-xorg-video-dummy
       - EMSCRIPTEN_BROWSER=firefox -profile tmp-firefox-profile/
       - EM_LACKS_SOUND_HARDWARE=1
       - EM_TESTRUNNER_DETECT_TEMPFILE_LEAKS=0