Bug 1552608 - Define AsyncCompositionManager::mFixedLayerMargins and its getter/setter on all platforms. r=tnikkel

It's still only used on Android, but keeping it and all code that interacts
with it inside an #ifdef is too much trouble for a tiny amount of space
saving.

Differential Revision: https://phabricator.services.mozilla.com/D48369

--HG--
extra : moz-landing-system : lando

gfx/layers/composite/AsyncCompositionManager.cpp

@@ -1226,10 +1226,7 @@ bool AsyncCompositionManager::ApplyAsyncContentTransformToTree(
               !layer->GetParent()->GetIsFixedPosition() &&
               IsFixedToZoomContainer(layer)) {
             LayerToParentLayerMatrix4x4 emptyTransform;
-            ScreenMargin marginsForFixedLayer;
-#ifdef MOZ_WIDGET_ANDROID
-            marginsForFixedLayer = GetFixedLayerMargins();
-#endif
+            ScreenMargin marginsForFixedLayer = GetFixedLayerMargins();
             AdjustFixedOrStickyLayer(zoomContainer, layer,
                                      sampler->GetGuid(*zoomedMetrics).mScrollId,
                                      emptyTransform, emptyTransform,
@@ -1473,7 +1470,6 @@ bool AsyncCompositionManager::TransformShadowTree(
   return wantNextFrame;
 }
 
-#if defined(MOZ_WIDGET_ANDROID)
 void AsyncCompositionManager::SetFixedLayerMargins(ScreenIntCoord aTop,
                                                    ScreenIntCoord aBottom) {
   mFixedLayerMargins.top = aTop;
@@ -1487,7 +1483,6 @@ ScreenMargin AsyncCompositionManager::GetFixedLayerMargins() const {
   }
   return result;
 }
-#endif  // defined(MOZ_WIDGET_ANDROID)
 
 }  // namespace layers
 }  // namespace mozilla

gfx/layers/composite/AsyncCompositionManager.h

@@ -234,11 +234,14 @@ class AsyncCompositionManager final {
 
   MOZ_NON_OWNING_REF CompositorBridgeParent* mCompositorBridge;
 
-#ifdef MOZ_WIDGET_ANDROID
  public:
   void SetFixedLayerMargins(ScreenIntCoord aTop, ScreenIntCoord aBottom);
   ScreenMargin GetFixedLayerMargins() const;
 
+ private:
+  ScreenMargin mFixedLayerMargins;
+
+#ifdef MOZ_WIDGET_ANDROID
  private:
   // This calculates whether frame metrics should be sent to Java.
   bool FrameMetricsHaveUpdated(const FrameMetrics& aMetrics);
@@ -249,7 +252,6 @@ class AsyncCompositionManager final {
   // then we need to reposition the gecko scrollbar to deal with the
   // dynamic toolbar shifting content around.
   ScrollableLayerGuid::ViewID mRootScrollableId;
-  ScreenMargin mFixedLayerMargins;
 #endif
 };