Split out the style-determined direct compositing reasons

Source/core/rendering/compositing/CompositingReasonFinder.cpp

Index: Source/core/rendering/compositing/CompositingReasonFinder.cpp
diff --git a/Source/core/rendering/compositing/CompositingReasonFinder.cpp b/Source/core/rendering/compositing/CompositingReasonFinder.cpp
index e2f80be02c3fa794eb4dd51cbb785e8d2d38cf0f..9054f3abc8c43278640edf1cee68b76a17e50fd2 100644
--- a/Source/core/rendering/compositing/CompositingReasonFinder.cpp
+++ b/Source/core/rendering/compositing/CompositingReasonFinder.cpp
@@ -59,9 +59,8 @@ bool CompositingReasonFinder::isMainFrame() const
     return !m_renderView.document().ownerElement();
 }
 
-CompositingReasons CompositingReasonFinder::directReasons(const RenderLayer* layer, bool* needToRecomputeCompositingRequirements) const
+CompositingReasons CompositingReasonFinder::styleDeterminedDirectReasons(RenderObject* renderer) const
 {
-    RenderObject* renderer = layer->renderer();
     CompositingReasons directReasons = CompositingReasonNone;
 
     if (requiresCompositingForTransform(renderer))
@@ -76,26 +75,41 @@ CompositingReasons CompositingReasonFinder::directReasons(const RenderLayer* lay
     if (requiresCompositingForFilters(renderer))
         directReasons |= CompositingReasonFilters;
 
-    if (requiresCompositingForPosition(renderer, layer, 0, needToRecomputeCompositingRequirements))
-        directReasons |= renderer->style()->position() == FixedPosition ? CompositingReasonPositionFixed : CompositingReasonPositionSticky;
+    if (requiresCompositingForWillChange(renderer))
+        directReasons |= CompositingReasonWillChange;
 
-    if (requiresCompositingForOverflowScrolling(layer))
-        directReasons |= CompositingReasonOverflowScrollingTouch;
+    directReasons |= renderer->additionalCompositingReasons(m_compositingTriggers);
 
-    if (requiresCompositingForOverflowScrollingParent(layer))
-        directReasons |= CompositingReasonOverflowScrollingParent;
+    ASSERT(!(directReasons & ~CompositingReasonComboAllStyleDeterminedDirectReasons));
+    return directReasons;
+}
+
+CompositingReasons CompositingReasonFinder::nonStyleDeterminedDirectReasons(const RenderLayer* layer, bool* needToRecomputeCompositingRequirements) const
+{
+    CompositingReasons directReasons = CompositingReasonNone;
 
     if (requiresCompositingForOutOfFlowClipping(layer))
         directReasons |= CompositingReasonOutOfFlowClipping;
 
-    if (requiresCompositingForWillChange(renderer))
-        directReasons |= CompositingReasonWillChange;
+    if (requiresCompositingForOverflowScrolling(layer))
+        directReasons |= CompositingReasonOverflowScrollingTouch;
 
-    directReasons |= renderer->additionalCompositingReasons(m_compositingTriggers);
+    if (requiresCompositingForOverflowScrollingParent(layer))
+        directReasons |= CompositingReasonOverflowScrollingParent;
 
+    RenderObject* renderer = layer->renderer();
+    if (requiresCompositingForPosition(renderer, layer, 0, needToRecomputeCompositingRequirements))
+        directReasons |= renderer->style()->position() == FixedPosition ? CompositingReasonPositionFixed : CompositingReasonPositionSticky;
+
+    ASSERT(!(directReasons & CompositingReasonComboAllStyleDeterminedDirectReasons));
     return directReasons;
 }
 
+CompositingReasons CompositingReasonFinder::directReasons(const RenderLayer* layer, bool* needToRecomputeCompositingRequirements) const
+{
+    return styleDeterminedDirectReasons(layer->renderer()) | nonStyleDeterminedDirectReasons(layer, needToRecomputeCompositingRequirements);
+}
+
 bool CompositingReasonFinder::requiresCompositingForScrollableFrame() const
 {
     // Need this done first to determine overflow.