Bug 1738926 Part 1: Check if sublayers need to be rebuilt. r=mstange

This fixes a correctness issue. Since NativeLayerCA Representations can
generate new CALayers under certain conditions, the NativeLayerRootCA must
check to see if a rebuild is necessary when committing.

Differential Revision: https://phabricator.services.mozilla.com/D131307

gfx/layers/NativeLayerCA.h

@@ -276,6 +276,7 @@ class NativeLayerCA : public NativeLayer {
   CALayer* UnderlyingCALayer(WhichRepresentation aRepresentation);
   void ApplyChanges(WhichRepresentation aRepresentation);
   bool HasUpdate(WhichRepresentation aRepresentation);
+  bool HasUpdateAffectingLayers(WhichRepresentation aRepresentation);
   void SetBackingScale(float aBackingScale);
 
   // Invalidates the specified region in all surfaces that are tracked by this

gfx/layers/NativeLayerCA.mm

@@ -335,6 +335,7 @@ void NativeLayerRootCA::Representation::Commit(WhichRepresentation aRepresentati
   // list of sublayers. The order is important because we need layer->UnderlyingCALayer()
   // to be non-null, and the underlying CALayer gets lazily initialized in ApplyChanges().
   for (auto layer : aSublayers) {
+    mustRebuild |= layer->HasUpdateAffectingLayers(aRepresentation);
     layer->ApplyChanges(aRepresentation);
   }
 
@@ -1194,6 +1195,11 @@ bool NativeLayerCA::HasUpdate(WhichRepresentation aRepresentation) {
   return GetRepresentation(aRepresentation).HasUpdate();
 }
 
+bool NativeLayerCA::HasUpdateAffectingLayers(WhichRepresentation aRepresentation) {
+  MutexAutoLock lock(mMutex);
+  return GetRepresentation(aRepresentation).mMutatedSpecializeVideo;
+}
+
 CALayer* NativeLayerCA::UnderlyingCALayer(WhichRepresentation aRepresentation) {
   MutexAutoLock lock(mMutex);
   return GetRepresentation(aRepresentation).UnderlyingCALayer();