Bug 1348408 - Only create inset box shadow WR layers for cases WR supports. r=rhunt

layout/painting/nsDisplayList.cpp

@@ -5114,6 +5114,29 @@ nsDisplayBoxShadowInner::GetLayerState(nsDisplayListBuilder* aBuilder,
                                        const ContainerLayerParameters& aParameters)
 {
   if (gfxPrefs::LayersAllowInsetBoxShadow()) {
+    nsPoint offset = ToReferenceFrame();
+    nsRect borderRect = nsRect(offset, mFrame->GetSize());
+    RectCornerRadii innerRadii;
+    bool hasBorderRadius = nsCSSRendering::GetShadowInnerRadii(mFrame,
+                                                               borderRect,
+                                                               innerRadii);
+    if (hasBorderRadius) {
+      return LAYER_NONE;
+    }
+
+    nsCSSShadowArray* shadows = mFrame->StyleEffects()->mBoxShadow;
+    for (uint32_t i = shadows->Length(); i > 0; --i) {
+      nsCSSShadowItem* shadowItem = shadows->ShadowAt(i - 1);
+      if (!shadowItem->mInset) {
+        continue;
+      }
+
+      if (shadowItem->mXOffset <= 0 || shadowItem->mYOffset <= 0) {
+        // Need to wait for WR to support clip out.
+        return LAYER_NONE;
+      }
+    }
+
     return LAYER_ACTIVE;
   }
 

layout/reftests/box-shadow/reftest.list

@@ -32,7 +32,7 @@ fuzzy(26,3610) == boxshadow-rotated.html boxshadow-rotated-ref.html # Bug 121126
 == boxshadow-inset-large-border-radius.html boxshadow-inset-large-border-radius-ref.html
 
 # fuzzy due to blur going inside, but as long as it's essentially black instead of a light gray its ok.
-fuzzy(12,9445) fuzzy-if(d2d,13,10926) == boxshadow-inset-large-offset.html boxshadow-inset-large-offset-ref.html
+fuzzy(13,9445) fuzzy-if(d2d,13,10926) fuzzy-if(webrender,13,13612) == boxshadow-inset-large-offset.html boxshadow-inset-large-offset-ref.html
 
 == overflow-not-scrollable-1.html overflow-not-scrollable-1-ref.html
 == overflow-not-scrollable-1.html overflow-not-scrollable-1-ref2.html