Bug 1301863 - Tell the JS engine how much memory blob reflectors hold alive r=baku

dom/bindings/BindingUtils.h

@@ -2819,6 +2819,18 @@ ToSupportsIsOnPrimaryInheritanceChain(T* aObject, nsWrapperCache* aCache)
                                                                      aCache);
 }
 
+// Get the size of allocated memory to associate with a binding JSObject for a
+// native object. This is supplied to the JS engine to allow it to schedule GC
+// when necessary.
+//
+// This function supplies a default value and is overloaded for specific native
+// object types.
+inline uint64_t
+BindingJSObjectMallocBytes(void *aNativePtr)
+{
+  return 0;
+}
+
 // The BindingJSObjectCreator class is supposed to be used by a caller that
 // wants to create and initialise a binding JSObject. After initialisation has
 // been successfully completed it should call ForgetObject().
@@ -2861,6 +2873,10 @@ public:
       mNative = aNative;
       mReflector = aReflector;
     }
+
+    if (uint64_t mallocBytes = BindingJSObjectMallocBytes(aNative)) {
+      JS_updateMallocCounter(aCx, mallocBytes);
+    }
   }
 
   void
@@ -2874,6 +2890,10 @@ public:
       mNative = aNative;
       mReflector = aReflector;
     }
+
+    if (uint64_t mallocBytes = BindingJSObjectMallocBytes(aNative)) {
+      JS_updateMallocCounter(aCx, mallocBytes);
+    }
   }
 
   void

dom/canvas/CanvasRenderingContextHelper.cpp

@@ -40,19 +40,9 @@ CanvasRenderingContextHelper::ToBlob(JSContext* aCx,
     {
       RefPtr<Blob> blob = aBlob;
 
-      ErrorResult rv;
-      uint64_t size = blob->GetSize(rv);
-      if (rv.Failed()) {
-        rv.SuppressException();
-      } else {
-        AutoJSAPI jsapi;
-        if (jsapi.Init(mGlobal)) {
-          JS_updateMallocCounter(jsapi.cx(), size);
-        }
-      }
-
       RefPtr<Blob> newBlob = Blob::Create(mGlobal, blob->Impl());
 
+      ErrorResult rv;
       mBlobCallback->Call(newBlob, rv);
 
       mGlobal = nullptr;

dom/canvas/OffscreenCanvas.cpp

@@ -266,17 +266,6 @@ OffscreenCanvas::ToBlob(JSContext* aCx,
     {
       RefPtr<Blob> blob = aBlob;
 
-      ErrorResult rv;
-      uint64_t size = blob->GetSize(rv);
-      if (rv.Failed()) {
-        rv.SuppressException();
-      } else {
-        AutoJSAPI jsapi;
-        if (jsapi.Init(mGlobal)) {
-          JS_updateMallocCounter(jsapi.cx(), size);
-        }
-      }
-
       if (mPromise) {
         RefPtr<Blob> newBlob = Blob::Create(mGlobal, blob->Impl());
         mPromise->MaybeResolve(newBlob);
@@ -285,7 +274,7 @@ OffscreenCanvas::ToBlob(JSContext* aCx,
       mGlobal = nullptr;
       mPromise = nullptr;
 
-      return rv.StealNSResult();
+      return NS_OK;
     }
 
     nsCOMPtr<nsIGlobalObject> mGlobal;

dom/file/BaseBlobImpl.h

@@ -97,6 +97,11 @@ public:
 
   virtual void GetType(nsAString& aType) override;
 
+  size_t GetAllocationSize() const override
+  {
+    return 0;
+  }
+
   virtual uint64_t GetSerialNumber() const override { return mSerialNumber; }
 
   virtual already_AddRefed<BlobImpl>

dom/file/Blob.cpp

@@ -214,6 +214,12 @@ Blob::Slice(const Optional<int64_t>& aStart,
   return blob.forget();
 }
 
+size_t
+Blob::GetAllocationSize() const
+{
+  return mImpl->GetAllocationSize();
+}
+
 NS_IMETHODIMP
 Blob::GetSendInfo(nsIInputStream** aBody,
                   uint64_t* aContentLength,
@@ -286,5 +292,12 @@ Blob::GetInternalStream(nsIInputStream** aStream, ErrorResult& aRv)
   mImpl->GetInternalStream(aStream, aRv);
 }
 
+uint64_t
+BindingJSObjectMallocBytes(Blob* aBlob)
+{
+  MOZ_ASSERT(aBlob);
+  return aBlob->GetAllocationSize();
+}
+
 } // namespace dom
 } // namespace mozilla

dom/file/Blob.h

@@ -130,6 +130,8 @@ public:
                                const nsAString& aContentType,
                                ErrorResult& aRv);
 
+  size_t GetAllocationSize() const;
+
 protected:
   // File constructor should never be used directly. Use Blob::Create instead.
   Blob(nsISupports* aParent, BlobImpl* aImpl);
@@ -147,6 +149,10 @@ private:
   nsCOMPtr<nsISupports> mParent;
 };
 
+// Override BindingJSObjectMallocBytes for blobs to tell the JS GC how much
+// memory is held live by the binding object.
+uint64_t BindingJSObjectMallocBytes(Blob* aBlob);
+
 } // namespace dom
 } // namespace mozilla
 

dom/file/BlobImpl.h

@@ -51,6 +51,8 @@ public:
 
   virtual void GetType(nsAString& aType) = 0;
 
+  virtual size_t GetAllocationSize() const = 0;
+
   /**
    * An effectively-unique serial number identifying this instance of FileImpl.
    *

dom/file/MemoryBlobImpl.h

@@ -53,6 +53,11 @@ public:
     return true;
   }
 
+  size_t GetAllocationSize() const override
+  {
+    return mLength;
+  }
+
   class DataOwner final : public mozilla::LinkedListElement<DataOwner>
   {
   public:

dom/file/MultipartBlobImpl.cpp

@@ -411,3 +411,13 @@ MultipartBlobImpl::MayBeClonedToOtherThreads() const
 
   return true;
 }
+
+size_t MultipartBlobImpl::GetAllocationSize() const
+{
+  size_t total = 0;
+  for (uint32_t i = 0; i < mBlobImpls.Length(); ++i) {
+    total += mBlobImpls[i]->GetAllocationSize();
+  }
+
+  return total;
+}

dom/file/MultipartBlobImpl.h

@@ -92,6 +92,8 @@ public:
 
   virtual bool MayBeClonedToOtherThreads() const override;
 
+  size_t GetAllocationSize() const override;
+
 protected:
   MultipartBlobImpl(nsTArray<RefPtr<BlobImpl>>&& aBlobImpls,
                     const nsAString& aName,

dom/file/StreamBlobImpl.cpp

@@ -156,5 +156,17 @@ StreamBlobImpl::CollectReports(nsIHandleReportCallback* aHandleReport,
   return NS_OK;
 }
 
+size_t
+StreamBlobImpl::GetAllocationSize() const
+{
+  nsCOMPtr<nsIStringInputStream> stringInputStream =
+    do_QueryInterface(mInputStream);
+  if (!stringInputStream) {
+    return 0;
+  }
+
+  return stringInputStream->SizeOfIncludingThis(MallocSizeOf);
+}
+
 } // namespace dom
 } // namespace mozilla

dom/file/StreamBlobImpl.h

@@ -77,6 +77,8 @@ public:
     return mIsDirectory;
   }
 
+  size_t GetAllocationSize() const override;
+
 private:
   StreamBlobImpl(nsIInputStream* aInputStream,
                  const nsAString& aContentType,

dom/file/StringBlobImpl.h

@@ -32,6 +32,11 @@ public:
   CreateSlice(uint64_t aStart, uint64_t aLength,
               const nsAString& aContentType, ErrorResult& aRv) override;
 
+  size_t GetAllocationSize() const override
+  {
+    return mData.Length();
+  }
+
 private:
   StringBlobImpl(const nsACString& aData, const nsAString& aContentType);
 

dom/html/HTMLCanvasElement.cpp

@@ -942,11 +942,6 @@ HTMLCanvasElement::MozGetAsFileImpl(const nsAString& aName,
   rv = NS_ReadInputStreamToBuffer(stream, &imgData, (uint32_t)imgSize);
   NS_ENSURE_SUCCESS(rv, rv);
 
-  JSContext* cx = nsContentUtils::GetCurrentJSContext();
-  if (cx) {
-    JS_updateMallocCounter(cx, imgSize);
-  }
-
   nsCOMPtr<nsPIDOMWindowInner> win = do_QueryInterface(OwnerDoc()->GetScopeObject());
 
   // The File takes ownership of the buffer

dom/indexedDB/FileSnapshot.h

@@ -108,6 +108,12 @@ private:
     mBlobImpl->GetType(aType);
   }
 
+  size_t
+  GetAllocationSize() const override
+  {
+    return mBlobImpl->GetAllocationSize();
+  }
+
   virtual uint64_t
   GetSerialNumber() const override
   {