Extract external file systems handling from isolated context.

webkit/fileapi/file_system_url_unittest.cc

Index: webkit/fileapi/file_system_url_unittest.cc
diff --git a/webkit/fileapi/file_system_url_unittest.cc b/webkit/fileapi/file_system_url_unittest.cc
index c6608ccf897488f6c5064b053fee9d220ae4f109..06db9236e6f2756a8544cad5c49b09ea1aa39820 100644
--- a/webkit/fileapi/file_system_url_unittest.cc
+++ b/webkit/fileapi/file_system_url_unittest.cc
@@ -7,6 +7,7 @@
 #include "base/file_path.h"
 #include "googleurl/src/gurl.h"
 #include "testing/gtest/include/gtest/gtest.h"
+#include "webkit/fileapi/external_mount_points.h"
 #include "webkit/fileapi/file_system_types.h"
 #include "webkit/fileapi/file_system_util.h"
 #include "webkit/fileapi/isolated_context.h"
@@ -214,7 +215,7 @@ TEST(FileSystemURLTest, DebugString) {
             NormalizedUTF8Path(kPath),
             kURL1.DebugString());
 
-  const FilePath kRoot(FPL("root"));
+  const FilePath kRoot(FPL("/root"));
   ScopedExternalFileSystem scoped_fs("foo", kFileSystemTypeNativeLocal, kRoot);
   const FileSystemURL kURL2(kOrigin, kFileSystemTypeExternal,
                             scoped_fs.GetVirtualRootPath().Append(kPath));