libjingle_unittest now compiles and passes on iOS! (reland of r5986)

Example run from cmd-line:
ninja -C out_ios/Debug-iphoneos libjingle_unittest && \
  ~/src/ios-deploy/ios-deploy -d -u -v -b \
    ~/src/wr/trunk/out_ios/Debug-iphoneos/libjingle_unittest.app

Note that the test's use of signals means that lldb will break in the middle
of the suite.  To ignore these signals tell lldb:

pro hand -p true -s false -n false SIGINT
pro hand -p true -s false -n false SIGTERM
continue

BUG=3241
R=kjellander@webrtc.org, tkchin@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/21369004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6025 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/talk/base/unixfilesystem.h b/talk/base/unixfilesystem.h
index aa9c920..d709115 100644
--- a/talk/base/unixfilesystem.h
+++ b/talk/base/unixfilesystem.h
@@ -36,13 +36,17 @@
 
 class UnixFilesystem : public FilesystemInterface {
  public:
+  UnixFilesystem();
+  virtual ~UnixFilesystem();
 
 #if defined(ANDROID) || defined(IOS)
-// Android does not have a native code API to fetch the app data or temp
-// folders. That needs to be passed into this class from Java. Similarly, iOS
-// only supports an Objective-C API for fetching the folder locations, so that
-// needs to be passed in here from Objective-C.
-
+  // Android does not have a native code API to fetch the app data or temp
+  // folders. That needs to be passed into this class from Java. Similarly, iOS
+  // only supports an Objective-C API for fetching the folder locations, so that
+  // needs to be passed in here from Objective-C.  Or at least that used to be
+  // the case; now the ctor will do the work if necessary and possible.
+  // TODO(fischman): add an Android version that uses JNI and drop the
+  // SetApp*Folder() APIs once external users stop using them.
   static void SetAppDataFolder(const std::string& folder);
   static void SetAppTempFolder(const std::string& folder);
 #endif