Refactoring RenderLayerCompositor to avoid redundant checks for Compositing reasons

Source/core/rendering/RenderLayerCompositor.cpp

Index: Source/core/rendering/RenderLayerCompositor.cpp
diff --git a/Source/core/rendering/RenderLayerCompositor.cpp b/Source/core/rendering/RenderLayerCompositor.cpp
index f472d127bcb8eb2dfaba789a65cf4fab397f1700..dd4213d8d72325d6edda73de91047d626d054ac7 100644
--- a/Source/core/rendering/RenderLayerCompositor.cpp
+++ b/Source/core/rendering/RenderLayerCompositor.cpp
@@ -1574,16 +1574,14 @@ CompositingReasons RenderLayerCompositor::directReasonsForCompositing(const Rend
     if (requiresCompositingForTransform(renderer))
         directReasons |= CompositingReason3DTransform;
 
+    // Only zero or one of the following conditions will be true for a given RenderLayer.
     if (requiresCompositingForVideo(renderer))
         directReasons |= CompositingReasonVideo;
-
-    if (requiresCompositingForCanvas(renderer))
+    else if (requiresCompositingForCanvas(renderer))
         directReasons |= CompositingReasonCanvas;
-
-    if (requiresCompositingForPlugin(renderer))
+    else if (requiresCompositingForPlugin(renderer))
         directReasons |= CompositingReasonPlugin;
-
-    if (requiresCompositingForFrame(renderer))
+    else if (requiresCompositingForFrame(renderer))
         directReasons |= CompositingReasonIFrame;
     
     if (requiresCompositingForBackfaceVisibilityHidden(renderer))