Start migrating the disk cache to using FilePath.

net/disk_cache/disk_cache_test_base.h

Index: net/disk_cache/disk_cache_test_base.h
diff --git a/net/disk_cache/disk_cache_test_base.h b/net/disk_cache/disk_cache_test_base.h
index 13e866eec64ae2de725b62d9fadc549eb271ddaf..c198e229408d570b0a4281d2ac054dfe3e208e71 100644
--- a/net/disk_cache/disk_cache_test_base.h
+++ b/net/disk_cache/disk_cache_test_base.h
@@ -9,6 +9,8 @@
 #include "testing/gtest/include/gtest/gtest.h"
 #include "testing/platform_test.h"
 
+class FilePath;
+
 namespace disk_cache {
 
 class Backend;
@@ -90,7 +92,7 @@ class DiskCacheTestWithCache : public DiskCacheTest {
  private:
   void InitMemoryCache();
   void InitDiskCache();
-  void InitDiskCacheImpl(const std::wstring& path);
+  void InitDiskCacheImpl(const FilePath& path);
 };
 
 #endif  // NET_DISK_CACHE_DISK_CACHE_TEST_BASE_H_