Keep FileSystem API metadata in memory for incognito mode

BUG=93417
R=jsbell@chromium.org

Change-Id: Id4fe10024f59437ef2f1c67b74834cf444465516
Reviewed-on: https://chromium-review.googlesource.com/948702Reviewed-by: Joshua Bell <jsbell@chromium.org>
Commit-Queue: Jochen Eisinger <jochen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#541055}

content/browser/fileapi/DEPS

 include_rules = [
-  "+third_party/leveldatabase/src/include/leveldb",
+  "+third_party/leveldatabase",
 ]

content/browser/fileapi/browser_file_system_helper.cc

@@ -33,6 +33,7 @@
 #include "storage/browser/fileapi/file_system_url.h"
 #include "storage/browser/fileapi/isolated_context.h"
 #include "storage/browser/quota/quota_manager.h"
+#include "third_party/leveldatabase/leveldb_chrome.h"
 #include "url/gurl.h"
 #include "url/url_constants.h"
 
@@ -61,7 +62,11 @@ FileSystemOptions CreateBrowserFileSystemOptions(bool is_incognito) {
           switches::kAllowFileAccessFromFiles)) {
     additional_allowed_schemes.push_back(url::kFileScheme);
   }
-  return FileSystemOptions(profile_mode, additional_allowed_schemes, nullptr);
+  leveldb::Env* env_override = nullptr;
+  if (is_incognito)
+    env_override = leveldb_chrome::NewMemEnv(leveldb::Env::Default());
+  return FileSystemOptions(profile_mode, additional_allowed_schemes,
+                           env_override);
 }
 
 }  // namespace