Add isWritableFileEntry to the fileSystem API

content/browser/child_process_security_policy_impl.cc

Index: content/browser/child_process_security_policy_impl.cc
diff --git a/content/browser/child_process_security_policy_impl.cc b/content/browser/child_process_security_policy_impl.cc
index bf0fc0f24fcb7ba92ca8b2740cc58f199a084ba4..c2678ae4e2a86134269a61762e17f6840da11dd5 100644
--- a/content/browser/child_process_security_policy_impl.cc
+++ b/content/browser/child_process_security_policy_impl.cc
@@ -525,6 +525,14 @@ bool ChildProcessSecurityPolicyImpl::CanReadFileSystem(
                                      kReadFilePermissions);
 }
 
+bool ChildProcessSecurityPolicyImpl::CanReadWriteFileSystem(
+    int child_id, const std::string& filesystem_id) {
+  return HasPermissionsForFileSystem(child_id,
+                                     filesystem_id,
+                                     kReadFilePermissions |
+                                     kWriteFilePermissions);
+}
+
 bool ChildProcessSecurityPolicyImpl::HasPermissionsForFile(
     int child_id, const FilePath& file, int permissions) {
   base::AutoLock lock(lock_);