Bug 1986185. r=aosmond a=RyanVM

Differential Revision: https://phabricator.services.mozilla.com/D263287

gfx/layers/ipc/CanvasTranslator.cpp

@@ -187,6 +187,10 @@ mozilla::ipc::IPCResult CanvasTranslator::RecvInitTranslator(
   }
 
   // Use the first buffer as our current buffer.
+  if (aBufferHandles.IsEmpty()) {
+    Deactivate();
+    return IPC_FAIL(this, "No canvas buffer shared memory supplied.");
+  }
   mDefaultBufferSize = aBufferHandles[0].Size();
   auto handleIter = aBufferHandles.begin();
   mCurrentShmem.shmem = std::move(*handleIter).Map();
@@ -424,11 +428,19 @@ already_AddRefed<gfx::DataSourceSurface> CanvasTranslator::WaitForSurface(
 }
 
 void CanvasTranslator::RecycleBuffer() {
+  if (!mCurrentShmem.IsValid()) {
+    return;
+  }
+
   mCanvasShmems.emplace(std::move(mCurrentShmem));
   NextBuffer();
 }
 
 void CanvasTranslator::NextBuffer() {
+  if (mCanvasShmems.empty()) {
+    return;
+  }
+
   // Check and signal the writer when we finish with a buffer, because it
   // might have hit the buffer count limit and be waiting to use our old one.
   CheckAndSignalWriter();