Improve delete all dialog message

MyTracks/res/values/strings.xml

@@ -2173,10 +2173,17 @@ limitations under the License.
   </string>
 
   <!-- Track Delete -->
-  <string name="track_delete_all_confirm_message"
+  <string name="track_delete_all_confirm_message_sync_off"
-    translation_description="When deleting all the tracks, the confirmation message.">
+    translation_description="When deleting all the tracks, the confirmation message when sync to
+      Google Drive is off.">
+    All tracks and markers will be permanently deleted from the device. Exported tracks on Google
+    Drive and external storage will not be deleted.
+  </string>
+  <string name="track_delete_all_confirm_message_sync_on"
+    translation_description="When deleting all the tracks, the confirmation message when sync to
+      Google Drive is on.">
     All tracks and markers will be permanently deleted from the device. Google Drive sync will be
-    turned off. No tracks will be deleted on Google Drive.
+    turned off. Exported tracks on Google Drive and external storage will not be deleted.
   </string>
   <string name="track_delete_one_confirm_message"
     translation_description="When deleting one track, the confirmation message.">

MyTracks/src/com/google/android/apps/mytracks/fragments/ConfirmDeleteDialogFragment.java

@@ -17,6 +17,7 @@
 package com.google.android.apps.mytracks.fragments;
 
 import com.google.android.apps.mytracks.util.DialogUtils;
+import com.google.android.apps.mytracks.util.PreferencesUtils;
 import com.google.android.maps.mytracks.R;
 
 import android.app.Activity;
@@ -84,8 +85,11 @@ public class ConfirmDeleteDialogFragment extends AbstractMyTracksDialogFragment
     int titleId;
     int messageId;
     if (trackIds.length == 1 && trackIds[0] == -1L) {
+      boolean driveSync = PreferencesUtils.getBoolean(
+          getActivity(), R.string.drive_sync_key, PreferencesUtils.DRIVE_SYNC_DEFAULT);
       titleId = R.string.generic_delete_all_confirm_title;
-      messageId = R.string.track_delete_all_confirm_message;
+      messageId = driveSync ? R.string.track_delete_all_confirm_message_sync_on
+          : R.string.track_delete_all_confirm_message_sync_off;
     } else {
       titleId = trackIds.length > 1 ? R.string.generic_delete_selected_confirm_title
           : R.string.track_delete_one_confirm_title;