Fixes crash when root dir does not exist.

Bug: 2904439
Change-Id: I629f88626e165348dd414f3ad49d9b415ab336cf

tests/DumpRenderTree2/src/com/android/dumprendertree2/TestsListPreloaderThread.java

@@ -68,15 +68,15 @@ public class TestsListPreloaderThread extends Thread {
         File file = new File(TESTS_ROOT_DIR_PATH, mRelativePath);
         if (!file.exists()) {
             Log.e(LOG_TAG + "::run", "Path does not exist: " + mRelativePath);
-            return;
+        } else {
+            /** Populate the tests' list accordingly */
+            if (file.isDirectory()) {
+                preloadTests(mRelativePath);
+            } else {
+                mTestsList.add(mRelativePath);
+            }
         }
 
-        /** Populate the tests' list accordingly */
-        if (file.isDirectory()) {
-            preloadTests(mRelativePath);
-        } else {
-            mTestsList.add(mRelativePath);
-        }
         mDoneMsg.obj = mTestsList;
         mDoneMsg.sendToTarget();
     }

tests/DumpRenderTree2/src/com/android/dumprendertree2/ui/DirListActivity.java

@@ -378,6 +378,10 @@ public class DirListActivity extends ListActivity {
     private ListItem[] getDirList(String dirPath) {
         File dir = new File(mRootDirPath, dirPath);
 
+        if (!dir.exists()) {
+            return new ListItem[0];
+        }
+
         List<ListItem> subDirs = new ArrayList<ListItem>();
         List<ListItem> subFiles = new ArrayList<ListItem>();