[SPARK-13142][WEB UI] Problem accessing Web UI /logPage/ on Microsoft Windows

Due to being on a Windows platform I have been unable to run the tests as described in the "Contributing to Spark" instructions. As the change is only to two lines of code in the Web UI, which I have manually built and tested, I am submitting this pull request anyway. I hope this is OK.

Is it worth considering also including this fix in any future 1.5.x releases (if any)?

I confirm this is my own original work and license it to the Spark project under its open source license.

Author: markpavey <mark.pavey@thefilter.com>

Closes #11135 from markpavey/JIRA_SPARK-13142_WindowsWebUILogFix.

core/src/main/scala/org/apache/spark/deploy/worker/ui/LogPage.scala

@@ -30,7 +30,7 @@ import org.apache.spark.util.logging.RollingFileAppender
 
 private[ui] class LogPage(parent: WorkerWebUI) extends WebUIPage("logPage") with Logging {
   private val worker = parent.worker
-  private val workDir = parent.workDir
+  private val workDir = new File(parent.workDir.toURI.normalize().getPath)
   private val supportedLogTypes = Set("stderr", "stdout")
 
   def renderLog(request: HttpServletRequest): String = {
@@ -138,7 +138,7 @@ private[ui] class LogPage(parent: WorkerWebUI) extends WebUIPage("logPage") with
     }
 
     // Verify that the normalized path of the log directory is in the working directory
-    val normalizedUri = new URI(logDirectory).normalize()
+    val normalizedUri = new File(logDirectory).toURI.normalize()
     val normalizedLogDir = new File(normalizedUri.getPath)
     if (!Utils.isInDirectory(workDir, normalizedLogDir)) {
       return ("Error: invalid log directory " + logDirectory, 0, 0, 0)