[fsp] Let extensions decide about the file system id.

chrome/browser/chromeos/file_system_provider/operations/read_directory_unittest.cc

Index: chrome/browser/chromeos/file_system_provider/operations/read_directory_unittest.cc
diff --git a/chrome/browser/chromeos/file_system_provider/operations/read_directory_unittest.cc b/chrome/browser/chromeos/file_system_provider/operations/read_directory_unittest.cc
index 1158ddf129118bba5ac6513a2352bf52579676f9..a53a8b6cf2c3c347baefd0e6895dc80c9c147fa1 100644
--- a/chrome/browser/chromeos/file_system_provider/operations/read_directory_unittest.cc
+++ b/chrome/browser/chromeos/file_system_provider/operations/read_directory_unittest.cc
@@ -9,6 +9,7 @@
 #include "base/json/json_reader.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/scoped_vector.h"
+#include "base/values.h"
 #include "chrome/browser/chromeos/file_system_provider/operations/read_directory.h"
 #include "chrome/common/extensions/api/file_system_provider.h"
 #include "chrome/common/extensions/api/file_system_provider_internal.h"
@@ -22,7 +23,7 @@ namespace operations {
 namespace {
 
 const char kExtensionId[] = "mbflcebpggnecokmikipoihdbecnjfoj";
-const int kFileSystemId = 1;
+const char kFileSystemId[] = "testing-file-system";
 const int kRequestId = 2;
 const base::FilePath::CharType kDirectoryPath[] = "/directory";
 
@@ -137,8 +138,8 @@ TEST_F(FileSystemProviderOperationsReadDirectoryTest, Execute) {
   base::ListValue* event_args = event->event_args.get();
   ASSERT_EQ(3u, event_args->GetSize());
 
-  int event_file_system_id = -1;
-  EXPECT_TRUE(event_args->GetInteger(0, &event_file_system_id));
+  std::string event_file_system_id;
+  EXPECT_TRUE(event_args->GetString(0, &event_file_system_id));
   EXPECT_EQ(kFileSystemId, event_file_system_id);
 
   int event_request_id = -1;
@@ -190,8 +191,8 @@ TEST_F(FileSystemProviderOperationsReadDirectoryTest, OnSuccess) {
   // base::Value.
   const std::string input =
       "[\n"
-      "  1,\n"  // kFileSystemId
-      "  2,\n"  // kRequestId
+      "  \"testing-file-system\",\n"  // kFileSystemId
+      "  2,\n"                        // kRequestId
       "  [\n"
       "    {\n"
       "      \"isDirectory\": false,\n"