Bug 1394695 - Don't push scrolling clips in layers-free WR if APZ is disabled. r=mstange

MozReview-Commit-ID: AesXui61mB2

--HG--
extra : rebase_source : bd8d1adacb3be142cc5227e9bae347abf0ddc14d

gfx/layers/wr/ScrollingLayersHelper.cpp

@@ -89,7 +89,8 @@ ScrollingLayersHelper::ScrollingLayersHelper(WebRenderLayer* aLayer,
 ScrollingLayersHelper::ScrollingLayersHelper(nsDisplayItem* aItem,
                                              wr::DisplayListBuilder& aBuilder,
                                              const StackingContextHelper& aStackingContext,
-                                             WebRenderLayerManager::ClipIdMap& aCache)
+                                             WebRenderLayerManager::ClipIdMap& aCache,
+                                             bool aApzEnabled)
   : mLayer(nullptr)
   , mBuilder(&aBuilder)
   , mPushedLayerLocalClip(false)
@@ -97,6 +98,14 @@ ScrollingLayersHelper::ScrollingLayersHelper(nsDisplayItem* aItem,
 {
   int32_t auPerDevPixel = aItem->Frame()->PresContext()->AppUnitsPerDevPixel();
 
+  if (!aApzEnabled) {
+    // If APZ is not enabled, we can ignore all the stuff with ASRs; we just
+    // need to define the clip chain on the item and that's it.
+    DefineAndPushChain(aItem->GetClipChain(), aBuilder, aStackingContext,
+        auPerDevPixel, aCache);
+    return;
+  }
+
   // There are two ASR chains here that we need to be fully defined. One is the
   // ASR chain pointed to by aItem->GetActiveScrolledRoot(). The other is the
   // ASR chain pointed to by aItem->GetClipChain()->mASR. We pick the leafmost

gfx/layers/wr/ScrollingLayersHelper.h

@@ -33,7 +33,8 @@ public:
   ScrollingLayersHelper(nsDisplayItem* aItem,
                         wr::DisplayListBuilder& aBuilder,
                         const StackingContextHelper& aStackingContext,
-                        WebRenderLayerManager::ClipIdMap& aCache);
+                        WebRenderLayerManager::ClipIdMap& aCache,
+                        bool aApzEnabled);
   ~ScrollingLayersHelper();
 
 private:

gfx/layers/wr/WebRenderLayerManager.cpp

@@ -328,7 +328,7 @@ WebRenderLayerManager::CreateWebRenderCommandsFromDisplayList(nsDisplayList* aDi
     }
 
     { // scope the ScrollingLayersHelper
-      ScrollingLayersHelper clip(item, aBuilder, aSc, mClipIdCache);
+      ScrollingLayersHelper clip(item, aBuilder, aSc, mClipIdCache, AsyncPanZoomEnabled());
 
       // Note: this call to CreateWebRenderCommands can recurse back into
       // this function if the |item| is a wrapper for a sublist.