[grid] Mounting dev/shm to browser containers.

This avoids pages crashing

Author: diemol

java/server/src/org/openqa/selenium/grid/docker/DockerSessionFactory.java

@@ -147,9 +147,12 @@ public Optional<ActiveSession> apply(CreateSessionRequest sessionRequest) {
       LOG.info("Creating container, mapping container port 4444 to " + port);
       Map<String, String> browserContainerEnvVars =
         getBrowserContainerEnvVars(sessionRequest.getCapabilities());
+      Map<String, String> devShmMount =
+        Collections.singletonMap("/dev/shm", "/dev/shm");
         Container container = docker.create(
           image(browserImage)
             .env(browserContainerEnvVars)
+            .bind(devShmMount)
             .map(Port.tcp(4444), Port.tcp(port)));
       container.start();
       ContainerInfo containerInfo = container.inspect();