Bug 1636731 - Use FunctionRef for animation generation enumeration. r=hiro

I see the allocation and deallocation of the std::function show up in
profiles.

Differential Revision: https://phabricator.services.mozilla.com/D74551

gfx/layers/AnimationInfo.cpp

@@ -182,7 +182,7 @@ Maybe<uint64_t> AnimationInfo::GetGenerationFromFrame(
 void AnimationInfo::EnumerateGenerationOnFrame(
     const nsIFrame* aFrame, const nsIContent* aContent,
     const CompositorAnimatableDisplayItemTypes& aDisplayItemTypes,
-    const AnimationGenerationCallback& aCallback) {
+    AnimationGenerationCallback aCallback) {
   if (XRE_IsContentProcess()) {
     if (nsIWidget* widget = nsContentUtils::WidgetForContent(aContent)) {
       // In case of child processes, we might not have yet created the layer

gfx/layers/AnimationInfo.h

@@ -11,6 +11,7 @@
 #include "nsDisplayItemTypes.h"
 #include "mozilla/Array.h"
 #include "mozilla/UniquePtr.h"
+#include "mozilla/FunctionRef.h"
 #include "mozilla/layers/LayersMessages.h"  // for TransformData
 
 struct RawServoAnimationValue;
@@ -102,7 +103,7 @@ class AnimationInfo final {
   using CompositorAnimatableDisplayItemTypes =
       Array<DisplayItemType,
             nsCSSPropertyIDSet::CompositorAnimatableDisplayItemCount()>;
-  using AnimationGenerationCallback = std::function<bool(
+  using AnimationGenerationCallback = FunctionRef<bool(
       const Maybe<uint64_t>& aGeneration, DisplayItemType aDisplayItemType)>;
   // Enumerates animation generations on |aFrame| for the given display item
   // types and calls |aCallback| with the animation generation.
@@ -111,7 +112,7 @@ class AnimationInfo final {
   static void EnumerateGenerationOnFrame(
       const nsIFrame* aFrame, const nsIContent* aContent,
       const CompositorAnimatableDisplayItemTypes& aDisplayItemTypes,
-      const AnimationGenerationCallback& aCallback);
+      AnimationGenerationCallback);
 
   void AddAnimationsForDisplayItem(nsIFrame* aFrame,
                                    nsDisplayListBuilder* aBuilder,

layout/painting/FrameLayerBuilder.cpp

@@ -6420,7 +6420,7 @@ Layer* FrameLayerBuilder::GetDedicatedLayer(nsIFrame* aFrame,
 
 /* static */
 void FrameLayerBuilder::EnumerateGenerationForDedicatedLayers(
-    const nsIFrame* aFrame, const AnimationGenerationCallback& aCallback) {
+    const nsIFrame* aFrame, AnimationGenerationCallback aCallback) {
   std::bitset<static_cast<uint32_t>(DisplayItemType::TYPE_MAX)> notFoundTypes;
   for (auto displayItemType : LayerAnimationInfo::sDisplayItemTypes) {
     notFoundTypes.set(static_cast<uint32_t>(displayItemType));

layout/painting/FrameLayerBuilder.h

@@ -500,7 +500,7 @@ class FrameLayerBuilder : public layers::LayerUserData {
   static Layer* GetDedicatedLayer(nsIFrame* aFrame,
                                   DisplayItemType aDisplayItemType);
 
-  using AnimationGenerationCallback = std::function<bool(
+  using AnimationGenerationCallback = FunctionRef<bool(
       const Maybe<uint64_t>& aGeneration, DisplayItemType aDisplayItemType)>;
   /**
    * Enumerates layers for the all display item types that correspond to
@@ -512,7 +512,7 @@ class FrameLayerBuilder : public layers::LayerUserData {
    * The enumeration stops if |aCallback| returns false.
    */
   static void EnumerateGenerationForDedicatedLayers(
-      const nsIFrame* aFrame, const AnimationGenerationCallback& aCallback);
+      const nsIFrame* aFrame, AnimationGenerationCallback);
 
   /**
    * This callback must be provided to EndTransaction. The callback data