Bug 1030481 - Remove nsIMutable, r=smaug

nsIMutable is used only by DOM Blob/File. But Blobs are immutable by spec.
FileBlobImpl has a couple of lazy member values, but those are called when
the object is cloned in order to be sent to a different thread/process.

Differential Revision: https://phabricator.services.mozilla.com/D58946

--HG--
extra : moz-landing-system : lando

dom/base/StructuredCloneHolder.cpp

@@ -464,8 +464,6 @@ JSObject* ReadBlob(JSContext* aCx, uint32_t aIndex,
     // pointer while destructors are running.
     RefPtr<BlobImpl> blobImpl = aHolder->BlobImpls()[aIndex];
 
-    MOZ_ALWAYS_SUCCEEDS(blobImpl->SetMutable(false));
-
     RefPtr<Blob> blob = Blob::Create(aHolder->GlobalDuringRead(), blobImpl);
     if (NS_WARN_IF(!blob)) {
       return nullptr;
@@ -492,7 +490,6 @@ bool WriteBlob(JSStructuredCloneWriter* aWriter, Blob* aBlob,
   }
 
   RefPtr<BlobImpl> blobImpl = aBlob->Impl();
-  MOZ_ALWAYS_SUCCEEDS(blobImpl->SetMutable(false));
 
   // We store the position of the blobImpl in the array as index.
   if (JS_WriteUint32Pair(aWriter, SCTAG_DOM_BLOB,
@@ -604,8 +601,6 @@ JSObject* ReadFileList(JSContext* aCx, JSStructuredCloneReader* aReader,
       RefPtr<BlobImpl> blobImpl = aHolder->BlobImpls()[pos];
       MOZ_ASSERT(blobImpl->IsFile());
 
-      MOZ_ALWAYS_SUCCEEDS(blobImpl->SetMutable(false));
-
       RefPtr<File> file = File::Create(aHolder->GlobalDuringRead(), blobImpl);
       if (NS_WARN_IF(!file)) {
         return nullptr;
@@ -645,7 +640,6 @@ bool WriteFileList(JSStructuredCloneWriter* aWriter, FileList* aFileList,
 
   for (uint32_t i = 0; i < aFileList->Length(); ++i) {
     RefPtr<BlobImpl> blobImpl = aFileList->Item(i)->Impl();
-    MOZ_ALWAYS_SUCCEEDS(blobImpl->SetMutable(false));
     blobImpls.AppendElement(blobImpl);
   }
 
@@ -686,7 +680,6 @@ JSObject* ReadFormData(JSContext* aCx, JSStructuredCloneReader* aReader,
         MOZ_ASSERT(indexOrLengthOfString < aHolder->BlobImpls().Length());
 
         RefPtr<BlobImpl> blobImpl = aHolder->BlobImpls()[indexOrLengthOfString];
-        MOZ_ALWAYS_SUCCEEDS(blobImpl->SetMutable(false));
 
         RefPtr<Blob> blob = Blob::Create(aHolder->GlobalDuringRead(), blobImpl);
         if (NS_WARN_IF(!blob)) {
@@ -785,7 +778,6 @@ bool WriteFormData(JSStructuredCloneWriter* aWriter, FormData* aFormData,
         }
 
         RefPtr<BlobImpl> blobImpl = aValue.GetAsBlob()->Impl();
-        MOZ_ALWAYS_SUCCEEDS(blobImpl->SetMutable(false));
 
         closure->mHolder->BlobImpls().AppendElement(blobImpl);
         return true;

dom/file/BaseBlobImpl.cpp

@@ -98,32 +98,6 @@ nsresult BaseBlobImpl::GetSendInfo(nsIInputStream** aBody,
   return NS_OK;
 }
 
-nsresult BaseBlobImpl::GetMutable(bool* aMutable) const {
-  *aMutable = !mImmutable;
-  return NS_OK;
-}
-
-nsresult BaseBlobImpl::SetMutable(bool aMutable) {
-  nsresult rv = NS_OK;
-
-  NS_ENSURE_ARG(!mImmutable || !aMutable);
-
-  if (!mImmutable && !aMutable) {
-    // Force the content type and size to be cached
-    nsAutoString dummyString;
-    GetType(dummyString);
-
-    ErrorResult error;
-    GetSize(error);
-    if (NS_WARN_IF(error.Failed())) {
-      return error.StealNSResult();
-    }
-  }
-
-  mImmutable = !aMutable;
-  return rv;
-}
-
 /* static */
 uint64_t BaseBlobImpl::NextSerialNumber() {
   static Atomic<uint64_t> nextSerialNumber;

dom/file/BaseBlobImpl.h

@@ -19,7 +19,6 @@ class BaseBlobImpl : public BlobImpl {
                int64_t aLastModifiedDate)
       : mBlobImplType(aBlobImplType),
         mIsFile(true),
-        mImmutable(false),
         mContentType(aContentType),
         mName(aName),
         mStart(0),
@@ -34,7 +33,6 @@ class BaseBlobImpl : public BlobImpl {
                const nsAString& aContentType, uint64_t aLength)
       : mBlobImplType(aBlobImplType),
         mIsFile(true),
-        mImmutable(false),
         mContentType(aContentType),
         mName(aName),
         mStart(0),
@@ -49,7 +47,6 @@ class BaseBlobImpl : public BlobImpl {
                uint64_t aLength)
       : mBlobImplType(aBlobImplType),
         mIsFile(false),
-        mImmutable(false),
         mContentType(aContentType),
         mStart(0),
         mLength(aLength),
@@ -63,7 +60,6 @@ class BaseBlobImpl : public BlobImpl {
                uint64_t aStart, uint64_t aLength)
       : mBlobImplType(aBlobImplType),
         mIsFile(false),
-        mImmutable(false),
         mContentType(aContentType),
         mStart(aStart),
         mLength(aLength),
@@ -126,10 +122,6 @@ class BaseBlobImpl : public BlobImpl {
                                nsACString& aContentType,
                                nsACString& aCharset) override;
 
-  virtual nsresult GetMutable(bool* aMutable) const override;
-
-  virtual nsresult SetMutable(bool aMutable) override;
-
   virtual void SetLazyData(const nsAString& aName,
                            const nsAString& aContentType, uint64_t aLength,
                            int64_t aLastModifiedDate) override {
@@ -167,7 +159,6 @@ class BaseBlobImpl : public BlobImpl {
   const nsString mBlobImplType;
 
   bool mIsFile;
-  bool mImmutable;
 
   nsString mContentType;
   nsString mName;

dom/file/Blob.cpp

@@ -40,9 +40,8 @@ NS_IMPL_CYCLE_COLLECTION_TRACE_END
 
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(Blob)
   NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
-  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIMutable)
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
   NS_INTERFACE_MAP_ENTRY_CONCRETE(Blob)
-  NS_INTERFACE_MAP_ENTRY(nsIMutable)
   NS_INTERFACE_MAP_ENTRY(nsISupportsWeakReference)
 NS_INTERFACE_MAP_END
 
@@ -206,12 +205,6 @@ nsresult Blob::GetSendInfo(nsIInputStream** aBody, uint64_t* aContentLength,
   return mImpl->GetSendInfo(aBody, aContentLength, aContentType, aCharset);
 }
 
-NS_IMETHODIMP
-Blob::GetMutable(bool* aMutable) { return mImpl->GetMutable(aMutable); }
-
-NS_IMETHODIMP
-Blob::SetMutable(bool aMutable) { return mImpl->SetMutable(aMutable); }
-
 JSObject* Blob::WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto) {
   return Blob_Binding::Wrap(aCx, this, aGivenProto);
 }

dom/file/Blob.h

@@ -14,7 +14,6 @@
 #include "mozilla/dom/BodyConsumer.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsCOMPtr.h"
-#include "nsIMutable.h"
 #include "nsWrapperCache.h"
 #include "nsWeakReference.h"
 
@@ -36,14 +35,10 @@ class Promise;
     }                                                \
   }
 
-class Blob : public nsIMutable,
-             public nsSupportsWeakReference,
-             public nsWrapperCache {
+class Blob : public nsSupportsWeakReference, public nsWrapperCache {
  public:
-  NS_DECL_NSIMUTABLE
-
   NS_DECL_CYCLE_COLLECTING_ISUPPORTS_FINAL
-  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS_AMBIGUOUS(Blob, nsIMutable)
+  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(Blob)
   NS_DECLARE_STATIC_IID_ACCESSOR(NS_DOM_BLOB_IID)
 
   typedef OwningArrayBufferViewOrArrayBufferOrBlobOrUSVString BlobPart;
@@ -158,7 +153,7 @@ size_t BindingJSObjectMallocBytes(Blob* aBlob);
 }  // namespace mozilla
 
 inline nsISupports* ToSupports(mozilla::dom::Blob* aBlob) {
-  return static_cast<nsIMutable*>(aBlob);
+  return static_cast<nsISupportsWeakReference*>(aBlob);
 }
 
 #endif  // mozilla_dom_Blob_h

dom/file/BlobImpl.h

@@ -89,10 +89,6 @@ class BlobImpl : public nsISupports {
                                nsACString& aContentType,
                                nsACString& aCharset) = 0;
 
-  virtual nsresult GetMutable(bool* aMutable) const = 0;
-
-  virtual nsresult SetMutable(bool aMutable) = 0;
-
   virtual void SetLazyData(const nsAString& aName,
                            const nsAString& aContentType, uint64_t aLength,
                            int64_t aLastModifiedDate) = 0;

dom/file/EmptyBlobImpl.cpp

@@ -15,11 +15,6 @@ already_AddRefed<BlobImpl> EmptyBlobImpl::CreateSlice(
     ErrorResult& aRv) {
   MOZ_ASSERT(!aStart && !aLength);
   RefPtr<BlobImpl> impl = new EmptyBlobImpl(aContentType);
-
-  DebugOnly<bool> isMutable;
-  MOZ_ASSERT(NS_SUCCEEDED(impl->GetMutable(&isMutable)));
-  MOZ_ASSERT(!isMutable);
-
   return impl.forget();
 }
 

dom/file/EmptyBlobImpl.h

@@ -18,16 +18,12 @@ class EmptyBlobImpl final : public BaseBlobImpl {
 
   explicit EmptyBlobImpl(const nsAString& aContentType)
       : BaseBlobImpl(NS_LITERAL_STRING("EmptyBlobImpl"), aContentType,
-                     0 /* aLength */) {
-    mImmutable = true;
-  }
+                     0 /* aLength */) {}
 
   EmptyBlobImpl(const nsAString& aName, const nsAString& aContentType,
                 int64_t aLastModifiedDate)
       : BaseBlobImpl(NS_LITERAL_STRING("EmptyBlobImpl"), aName, aContentType, 0,
-                     aLastModifiedDate) {
-    mImmutable = true;
-  }
+                     aLastModifiedDate) {}
 
   virtual void CreateInputStream(nsIInputStream** aStream,
                                  ErrorResult& aRv) override;

dom/file/FileBlobImpl.cpp

@@ -21,6 +21,7 @@ namespace dom {
 FileBlobImpl::FileBlobImpl(nsIFile* aFile)
     : BaseBlobImpl(NS_LITERAL_STRING("FileBlobImpl"), EmptyString(),
                    EmptyString(), UINT64_MAX, INT64_MAX),
+      mMutex("FileBlobImpl::mMutex"),
       mFile(aFile),
       mFileId(-1),
       mWholeFile(true) {
@@ -37,6 +38,7 @@ FileBlobImpl::FileBlobImpl(const nsAString& aName,
                            nsIFile* aFile)
     : BaseBlobImpl(NS_LITERAL_STRING("FileBlobImpl"), aName, aContentType,
                    aLength, UINT64_MAX),
+      mMutex("FileBlobImpl::mMutex"),
       mFile(aFile),
       mFileId(-1),
       mWholeFile(true) {
@@ -50,6 +52,7 @@ FileBlobImpl::FileBlobImpl(const nsAString& aName,
                            nsIFile* aFile, int64_t aLastModificationDate)
     : BaseBlobImpl(NS_LITERAL_STRING("FileBlobImpl"), aName, aContentType,
                    aLength, aLastModificationDate),
+      mMutex("FileBlobImpl::mMutex"),
       mFile(aFile),
       mFileId(-1),
       mWholeFile(true) {
@@ -62,6 +65,7 @@ FileBlobImpl::FileBlobImpl(nsIFile* aFile, const nsAString& aName,
                            const nsAString& aContentType,
                            const nsAString& aBlobImplType)
     : BaseBlobImpl(aBlobImplType, aName, aContentType, UINT64_MAX, INT64_MAX),
+      mMutex("FileBlobImpl::mMutex"),
       mFile(aFile),
       mFileId(-1),
       mWholeFile(true) {
@@ -79,12 +83,12 @@ FileBlobImpl::FileBlobImpl(const FileBlobImpl* aOther, uint64_t aStart,
                            uint64_t aLength, const nsAString& aContentType)
     : BaseBlobImpl(NS_LITERAL_STRING("FileBlobImpl"), aContentType,
                    aOther->mStart + aStart, aLength),
+      mMutex("FileBlobImpl::mMutex"),
       mFile(aOther->mFile),
       mFileId(-1),
       mWholeFile(false) {
   MOZ_ASSERT(mFile, "must have file");
   MOZ_ASSERT(XRE_IsParentProcess());
-  mImmutable = aOther->mImmutable;
   mMozFullPath = aOther->mMozFullPath;
 }
 
@@ -100,6 +104,8 @@ void FileBlobImpl::GetMozFullPathInternal(nsAString& aFilename,
                                           ErrorResult& aRv) {
   MOZ_ASSERT(mIsFile, "Should only be called on files");
 
+  MutexAutoLock lock(mMutex);
+
   if (!mMozFullPath.IsVoid()) {
     aFilename = mMozFullPath;
     return;
@@ -114,6 +120,8 @@ void FileBlobImpl::GetMozFullPathInternal(nsAString& aFilename,
 }
 
 uint64_t FileBlobImpl::GetSize(ErrorResult& aRv) {
+  MutexAutoLock lock(mMutex);
+
   if (BaseBlobImpl::IsSizeUnknown()) {
     MOZ_ASSERT(mWholeFile,
                "Should only use lazy size when using the whole file");
@@ -134,14 +142,14 @@ uint64_t FileBlobImpl::GetSize(ErrorResult& aRv) {
   return mLength;
 }
 
-namespace {
-
-class GetTypeRunnable final : public WorkerMainThreadRunnable {
+class FileBlobImpl::GetTypeRunnable final : public WorkerMainThreadRunnable {
  public:
-  GetTypeRunnable(WorkerPrivate* aWorkerPrivate, BlobImpl* aBlobImpl)
+  GetTypeRunnable(WorkerPrivate* aWorkerPrivate, FileBlobImpl* aBlobImpl,
+                  const MutexAutoLock& aProofOfLock)
       : WorkerMainThreadRunnable(aWorkerPrivate,
                                  NS_LITERAL_CSTRING("FileBlobImpl :: GetType")),
-        mBlobImpl(aBlobImpl) {
+        mBlobImpl(aBlobImpl),
+        mProofOfLock(aProofOfLock) {
     MOZ_ASSERT(aBlobImpl);
     aWorkerPrivate->AssertIsOnWorkerThread();
   }
@@ -150,19 +158,24 @@ class GetTypeRunnable final : public WorkerMainThreadRunnable {
     MOZ_ASSERT(NS_IsMainThread());
 
     nsAutoString type;
-    mBlobImpl->GetType(type);
+    mBlobImpl->GetTypeInternal(type, mProofOfLock);
     return true;
   }
 
  private:
   ~GetTypeRunnable() = default;
 
-  RefPtr<BlobImpl> mBlobImpl;
+  RefPtr<FileBlobImpl> mBlobImpl;
+  const MutexAutoLock& mProofOfLock;
 };
 
-}  // anonymous namespace
-
 void FileBlobImpl::GetType(nsAString& aType) {
+  MutexAutoLock lock(mMutex);
+  GetTypeInternal(aType, lock);
+}
+
+void FileBlobImpl::GetTypeInternal(nsAString& aType,
+                                   const MutexAutoLock& aProofOfLock) {
   aType.Truncate();
 
   if (mContentType.IsVoid()) {
@@ -178,16 +191,15 @@ void FileBlobImpl::GetType(nsAString& aType) {
       }
 
       RefPtr<GetTypeRunnable> runnable =
-          new GetTypeRunnable(workerPrivate, this);
+          new GetTypeRunnable(workerPrivate, this, aProofOfLock);
 
       ErrorResult rv;
       runnable->Dispatch(Canceling, rv);
       if (NS_WARN_IF(rv.Failed())) {
         rv.SuppressException();
-      }
         return;
       }
-
+    } else {
       nsresult rv;
       nsCOMPtr<nsIMIMEService> mimeService =
           do_GetService(NS_MIMESERVICE_CONTRACTID, &rv);
@@ -204,12 +216,16 @@ void FileBlobImpl::GetType(nsAString& aType) {
       AppendUTF8toUTF16(mimeType, mContentType);
       mContentType.SetIsVoid(false);
     }
+  }
 
   aType = mContentType;
 }
 
 int64_t FileBlobImpl::GetLastModified(ErrorResult& aRv) {
   MOZ_ASSERT(mIsFile, "Should only be called on files");
+
+  MutexAutoLock lock(mMutex);
+
   if (BaseBlobImpl::IsDateUnknown()) {
     PRTime msecs;
     aRv = mFile->GetLastModifiedTime(&msecs);

dom/file/FileBlobImpl.h

@@ -8,6 +8,7 @@
 #define mozilla_dom_FileBlobImpl_h
 
 #include "mozilla/dom/BaseBlobImpl.h"
+#include "mozilla/Mutex.h"
 
 class nsIFile;
 
@@ -72,6 +73,18 @@ class FileBlobImpl : public BaseBlobImpl {
                                                  const nsAString& aContentType,
                                                  ErrorResult& aRv) override;
 
+  class GetTypeRunnable;
+  void GetTypeInternal(nsAString& aType, const MutexAutoLock& aProofOfLock);
+
+  // FileBlobImpl is the only BlobImpl with a few getter methods with lazy
+  // initialization. Because any BlobImpl must work thread-safe, we use a mutex.
+  // This is the list of the getter methods and the corresponding lazy members:
+  // - GetMozFullPathInternal - mMozFullPath
+  // - GetSize - mLength
+  // - GetType - mContentType
+  // - GetLastModified - mLastModificationDate
+  Mutex mMutex;
+
   nsCOMPtr<nsIFile> mFile;
   nsString mMozFullPath;
   int64_t mFileId;

dom/file/MemoryBlobImpl.h

@@ -147,7 +147,6 @@ class MemoryBlobImpl final : public BaseBlobImpl {
                      aOther->mStart + aStart, aLength),
         mDataOwner(aOther->mDataOwner) {
     MOZ_ASSERT(mDataOwner && mDataOwner->mData, "must have data");
-    mImmutable = aOther->mImmutable;
   }
 
   ~MemoryBlobImpl() {}

dom/file/MultipartBlobImpl.cpp

@@ -283,33 +283,6 @@ void MultipartBlobImpl::SetLengthAndModifiedDate(ErrorResult& aRv) {
   }
 }
 
-nsresult MultipartBlobImpl::SetMutable(bool aMutable) {
-  nsresult rv;
-
-  // This looks a little sketchy since BlobImpl objects are supposed to be
-  // threadsafe. However, we try to enforce that all BlobImpl objects must be
-  // set to immutable *before* being passed to another thread, so this should
-  // be safe.
-  if (!aMutable && !mImmutable && !mBlobImpls.IsEmpty()) {
-    for (uint32_t index = 0, count = mBlobImpls.Length(); index < count;
-         index++) {
-      rv = mBlobImpls[index]->SetMutable(aMutable);
-      if (NS_WARN_IF(NS_FAILED(rv))) {
-        return rv;
-      }
-    }
-  }
-
-  rv = BaseBlobImpl::SetMutable(aMutable);
-  if (NS_WARN_IF(NS_FAILED(rv))) {
-    return rv;
-  }
-
-  MOZ_ASSERT_IF(!aMutable, mImmutable);
-
-  return NS_OK;
-}
-
 bool MultipartBlobImpl::MayBeClonedToOtherThreads() const {
   for (uint32_t i = 0; i < mBlobImpls.Length(); ++i) {
     if (!mBlobImpls[i]->MayBeClonedToOtherThreads()) {

dom/file/MultipartBlobImpl.h

@@ -59,8 +59,6 @@ class MultipartBlobImpl final : public BaseBlobImpl {
     return mBlobImpls.Length() ? &mBlobImpls : nullptr;
   }
 
-  virtual nsresult SetMutable(bool aMutable) override;
-
   void SetName(const nsAString& aName) { mName = aName; }
 
   virtual bool MayBeClonedToOtherThreads() const override;

dom/file/StreamBlobImpl.cpp

@@ -50,9 +50,7 @@ StreamBlobImpl::StreamBlobImpl(already_AddRefed<nsIInputStream> aInputStream,
     : BaseBlobImpl(aBlobImplType, aContentType, aLength),
       mInputStream(std::move(aInputStream)),
       mIsDirectory(false),
-      mFileId(-1) {
-  mImmutable = true;
-}
+      mFileId(-1) {}
 
 StreamBlobImpl::StreamBlobImpl(already_AddRefed<nsIInputStream> aInputStream,
                                const nsAString& aName,
@@ -63,9 +61,7 @@ StreamBlobImpl::StreamBlobImpl(already_AddRefed<nsIInputStream> aInputStream,
                    aLastModifiedDate),
       mInputStream(std::move(aInputStream)),
       mIsDirectory(false),
-      mFileId(-1) {
-  mImmutable = true;
-}
+      mFileId(-1) {}
 
 StreamBlobImpl::~StreamBlobImpl() { UnregisterWeakMemoryReporter(this); }
 

dom/indexedDB/FileSnapshot.h

@@ -123,14 +123,6 @@ class BlobImplSnapshot final : public BlobImpl, public PIBlobImplSnapshot {
                                   aCharset);
   }
 
-  virtual nsresult GetMutable(bool* aMutable) const override {
-    return mBlobImpl->GetMutable(aMutable);
-  }
-
-  virtual nsresult SetMutable(bool aMutable) override {
-    return mBlobImpl->SetMutable(aMutable);
-  }
-
   virtual void SetLazyData(const nsAString& aName,
                            const nsAString& aContentType, uint64_t aLength,
                            int64_t aLastModifiedDate) override {

dom/url/URLWorker.cpp

@@ -29,10 +29,6 @@ class CreateURLRunnable : public WorkerMainThreadRunnable {
         mBlobImpl(aBlobImpl),
         mURL(aURL) {
     MOZ_ASSERT(aBlobImpl);
-
-    DebugOnly<bool> isMutable;
-    MOZ_ASSERT(NS_SUCCEEDED(aBlobImpl->GetMutable(&isMutable)));
-    MOZ_ASSERT(!isMutable);
   }
 
   bool MainThreadRun() override {
@@ -40,10 +36,6 @@ class CreateURLRunnable : public WorkerMainThreadRunnable {
 
     AssertIsOnMainThread();
 
-    DebugOnly<bool> isMutable;
-    MOZ_ASSERT(NS_SUCCEEDED(mBlobImpl->GetMutable(&isMutable)));
-    MOZ_ASSERT(!isMutable);
-
     nsCOMPtr<nsIPrincipal> principal = mWorkerPrivate->GetPrincipal();
 
     nsAutoCString url;
@@ -163,11 +155,6 @@ void URLWorker::CreateObjectURL(const GlobalObject& aGlobal, Blob& aBlob,
   RefPtr<BlobImpl> blobImpl = aBlob.Impl();
   MOZ_ASSERT(blobImpl);
 
-  aRv = blobImpl->SetMutable(false);
-  if (NS_WARN_IF(aRv.Failed())) {
-    return;
-  }
-
   RefPtr<CreateURLRunnable> runnable =
       new CreateURLRunnable(workerPrivate, blobImpl, aResult);
 

dom/xhr/XMLHttpRequestWorker.cpp

@@ -1893,14 +1893,6 @@ void XMLHttpRequestWorker::Send(
     RefPtr<Blob> blob = &aData.Value().GetAsBlob();
     MOZ_ASSERT(blob);
 
-    RefPtr<BlobImpl> blobImpl = blob->Impl();
-    MOZ_ASSERT(blobImpl);
-
-    aRv = blobImpl->SetMutable(false);
-    if (NS_WARN_IF(aRv.Failed())) {
-      return;
-    }
-
     JS::Rooted<JS::Value> value(aCx);
     if (!GetOrCreateDOMReflector(aCx, blob, &value)) {
       aRv.Throw(NS_ERROR_FAILURE);

xpcom/base/moz.build

@@ -18,7 +18,6 @@ XPIDL_SOURCES += [
     'nsIMemoryInfoDumper.idl',
     'nsIMemoryReporter.idl',
     'nsIMessageLoop.idl',
-    'nsIMutable.idl',
     'nsISecurityConsoleMessage.idl',
     'nsISupports.idl',
     'nsIUUIDGenerator.idl',

xpcom/base/nsIMutable.idl

@@ -1,22 +0,0 @@
-/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#include "nsISupports.idl"
-
-/**
- * nsIMutable defines an interface to be implemented by objects which
- * can be made immutable.
- */
-[scriptable, uuid(321578d0-03c1-4d95-8821-021ac612d18d)]
-interface nsIMutable : nsISupports
-{
-    /**
-     * Control whether or not this object can be modified.  If the flag is
-     * false, no modification is allowed.  Once the flag has been set to false,
-     * it cannot be reset back to true -- attempts to do so throw
-     * NS_ERROR_INVALID_ARG.
-     */
-    attribute boolean mutable;
-};

xpcom/build/XPCOM.h

@@ -77,7 +77,6 @@
 #include "nsIInputStream.h"
 #include "nsIInterfaceRequestor.h"
 #include "nsILineInputStream.h"
-#include "nsIMutable.h"
 #include "nsIObserver.h"
 #include "nsIObserverService.h"
 #include "nsIOutputStream.h"