Add wide string version of SetAnalyticsLibraryPath and export

"publicly".

Author: jonsimantov

analytics/src/analytics_desktop.cc

@@ -99,6 +99,14 @@ void SetAnalyticsLibraryPath(const char* path) {
     g_analytics_dll_filename = ANALYTICS_DLL_DEFAULT_FILENAME;
   }
 }
+
+void SetAnalyticsLibraryPath(const wchar_t* path) {
+  if (path) {
+    g_analytics_dll_filename = path;
+  } else {
+    g_analytics_dll_filename = ANALYTICS_DLL_DEFAULT_FILENAME;
+  }
+}
 #endif
 
 // Future data for analytics.

analytics/src/include/firebase/analytics.h

@@ -591,6 +591,22 @@ Future<int64_t> GetSessionId();
 /// app session.
 Future<int64_t> GetSessionIdLastResult();
 
+
+#ifdef INTERNAL_EXPERIMENTAL
+#if defined(_WIN32) || defined(DOXYGEN)
+/// Windows only: Specify the path to the Google Analytics Windows DLL.
+///
+/// @param path Path to the DLL, including filename, in UTF-8 format.
+void SetAnalyticsLibraryPath(const char* path);
+
+/// Windows only: Specify the path to the Google Analytics Windows DLL.
+///
+/// @param path Path to the DLL, including filename, in UTF-16 format.
+void SetAnalyticsLibraryPath(const wchar_t* path);
+#endif
+#endif
+
+  
 }  // namespace analytics
 }  // namespace firebase