--- a/dom/system/IOUtils.cpp
+++ b/dom/system/IOUtils.cpp
@@ -54,18 +54,17 @@
     if (nsresult _rv = (_file)->InitWithPath((_path)); NS_FAILED(_rv)) { \
       (_promise)->MaybeRejectWithOperationError(                         \
           FormatErrorMessage(_rv, "Could not parse path (%s)",           \
                              NS_ConvertUTF16toUTF8(_path).get()));       \
       return (_promise).forget();                                        \
     }                                                                    \
   } while (0)
 
-namespace mozilla {
-namespace dom {
+namespace mozilla::dom {
 
 // static helper functions
 
 /**
  * Platform-specific (e.g. Windows, Unix) implementations of XPCOM APIs may
  * report I/O errors inconsistently. For convenience, this function will attempt
  * to match a |nsresult| against known results which imply a file cannot be
  * found.
@@ -1412,13 +1411,12 @@ IOUtils::InternalWriteOpts::FromBinding(
           NS_ConvertUTF16toUTF8(aOptions.mTmpPath.Value()).get()));
     }
   }
 
   opts.mCompress = aOptions.mCompress;
   return opts;
 }
 
-}  // namespace dom
-}  // namespace mozilla
+}  // namespace mozilla::dom
 
 #undef REJECT_IF_SHUTTING_DOWN
 #undef REJECT_IF_INIT_PATH_FAILED

--- a/dom/system/IOUtils.h
+++ b/dom/system/IOUtils.h
@@ -402,21 +402,21 @@ class IOUtils::IOError {
  * for private use in the IOUtils implementation.
  *
  * Because web IDL dictionaries are not easily copy/moveable, this class is
  * used instead, until converted to the proper |mozilla::dom::FileInfo| before
  * returning any results to JavaScript.
  */
 struct IOUtils::InternalFileInfo {
   nsString mPath;
-  FileType mType;
-  uint64_t mSize;
-  uint64_t mLastModified;
+  FileType mType = FileType::Other;
+  uint64_t mSize = 0;
+  uint64_t mLastModified = 0;
   Maybe<uint64_t> mCreationTime;
-  uint32_t mPermissions;
+  uint32_t mPermissions = 0;
 };
 
 /**
  * This is an easier to work with representation of a
  * |mozilla::dom::WriteOptions| for private use in the |IOUtils|
  * implementation.
  *
  * Because web IDL dictionaries are not easily copy/moveable, this class is