Bug 1761483 - Limit chunk size in stream to avoid un-necessary OOM r=…

…smaug

Discovered that Windows 32-bit was having trouble with the test case on the bug,
and figured that it might be preferable to limit chunk size to something more
constrained.

Differential Revision: https://phabricator.services.mozilla.com/D142512

dom/base/BodyStream.cpp

@@ -554,10 +554,11 @@ void BodyStream::EnqueueChunkWithSizeIntoStream(JSContext* aCx,
                                                 ReadableStream* aStream,
                                                 uint64_t aAvailableData,
                                                 ErrorResult& aRv) {
-  // Because nsIInputStream can only read UINT32_MAX bytes in one go, limit
-  // ourselves to that for chunk size.
+  // To avoid OOMing up on huge amounts of available data on a 32 bit system,
+  // as well as potentially overflowing nsIInputStream's Read method's
+  // parameter, let's limit our maximum chunk size to 256MB.
   uint32_t ableToRead =
-      std::min(static_cast<uint64_t>(UINT32_MAX), aAvailableData);
+      std::min(static_cast<uint64_t>(256 * 1024 * 1024), aAvailableData);
 
   // Create Chunk
   aRv.MightThrowJSException();