Add SAL_DISABLE_GL_WATCHDOG env. var for obvious reasons.

Change-Id: Iec7cb6504a389972d8187954d5ed7aff94f2e01c
Reviewed-on: https://gerrit.libreoffice.org/18272Reviewed-by: Jan Holesovsky <kendy@collabora.com>
Tested-by: Jan Holesovsky <kendy@collabora.com>

vcl/README.vars

@@ -21,3 +21,4 @@ OpenGL
 SAL_FORCEGL - force enable OpenGL
 SAL_WITHOUT_WIDGET_CACHE - disable LRU caching of native widget texutres
 SAL_DISABLE_GLYPH_CACHING - don't render glyphs through OpenGL textures
+SAL_DISABLE_GL_WATCHDOG - don't start the thread that watches for broken GL drivers
\ No newline at end of file

vcl/source/opengl/OpenGLHelper.cxx

@@ -672,6 +672,7 @@ bool OpenGLHelper::isVCLOpenGLEnabled()
     }
     if (bRet)
     {
+        if (!getenv("SAL_DISABLE_GL_WATCHDOG"))
             OpenGLWatchdogThread::start();
         ImplGetSVData()->maWinData.mbNoSaveBackground = true;
     }