Convert recursion to iteration in clearClipRectsIncludingDescendants

BUG=674795
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2

Review-Url: https://codereview.chromium.org/2617903002
Cr-Commit-Position: refs/heads/master@{#442063}

third_party/WebKit/Source/core/paint/PaintLayerClipper.cpp

@@ -177,28 +177,32 @@ ClipRects& PaintLayerClipper::getClipRects(
   return storeClipRectsInCache(context, parentClipRects, *clipRects);
 }
 
-void PaintLayerClipper::clearClipRectsIncludingDescendants() {
+void PaintLayerClipper::clearCache(ClipRectsCacheSlot cacheSlot) {
+  if (cacheSlot == NumberOfClipRectsCacheSlots)
+    m_layer.clearClipRectsCache();
+  else if (ClipRectsCache* cache = m_layer.clipRectsCache())
+    cache->clear(cacheSlot);
+
   if (m_geometryMapper)
     m_geometryMapper.reset(new GeometryMapper);
-  m_layer.clearClipRectsCache();
+}
 
-  for (PaintLayer* layer = m_layer.firstChild(); layer;
-       layer = layer->nextSibling()) {
-    layer->clipper().clearClipRectsIncludingDescendants();
-  }
+void PaintLayerClipper::clearClipRectsIncludingDescendants() {
+  clearClipRectsIncludingDescendants(NumberOfClipRectsCacheSlots);
 }
 
 void PaintLayerClipper::clearClipRectsIncludingDescendants(
     ClipRectsCacheSlot cacheSlot) {
-  if (m_geometryMapper)
-    m_geometryMapper.reset(new GeometryMapper);
-
-  if (ClipRectsCache* cache = m_layer.clipRectsCache())
-    cache->clear(cacheSlot);
-
-  for (PaintLayer* layer = m_layer.firstChild(); layer;
-       layer = layer->nextSibling()) {
-    layer->clipper().clearClipRectsIncludingDescendants(cacheSlot);
+  std::stack<const PaintLayer*> layers;
+  layers.push(&m_layer);
+
+  while (!layers.empty()) {
+    const PaintLayer* currentLayer = layers.top();
+    layers.pop();
+    currentLayer->clipper().clearCache(cacheSlot);
+    for (const PaintLayer* layer = currentLayer->firstChild(); layer;
+         layer = layer->nextSibling())
+      layers.push(layer);
   }
 }
 

third_party/WebKit/Source/core/paint/PaintLayerClipper.h

@@ -200,6 +200,7 @@ class CORE_EXPORT PaintLayerClipper {
                                const LayoutSize& subpixelAccumulation) const;
 
  private:
+  void clearCache(ClipRectsCacheSlot);
   ClipRects& getClipRects(const ClipRectsContext&) const;
 
   void calculateClipRects(const ClipRectsContext&, ClipRects&) const;

third_party/WebKit/Source/core/paint/PaintLayerClipperTest.cpp

@@ -144,4 +144,92 @@ TEST_F(PaintLayerClipperTest, LocalClipRectFixedUnderTransform) {
             fixed->clipper().localClipRect(transformed));
 }
 
+TEST_F(PaintLayerClipperTest, ClearClipRectsRecursive) {
+  setBodyInnerHTML(
+      "<style>"
+      "div { "
+      "  width: 5px; height: 5px; background: blue;"
+      "  position: relative;"
+      "}"
+      "</style>"
+      "<div id='parent'>"
+      "  <div id='child'>"
+      "    <div id='grandchild'></div>"
+      "  </div>"
+      "</div>");
+
+  PaintLayer* parent =
+      toLayoutBoxModelObject(getLayoutObjectByElementId("parent"))->layer();
+  PaintLayer* child =
+      toLayoutBoxModelObject(getLayoutObjectByElementId("child"))->layer();
+
+  EXPECT_TRUE(parent->clipRectsCache());
+  EXPECT_TRUE(child->clipRectsCache());
+
+  parent->clipper().clearClipRectsIncludingDescendants();
+
+  EXPECT_FALSE(parent->clipRectsCache());
+  EXPECT_FALSE(child->clipRectsCache());
+}
+
+TEST_F(PaintLayerClipperTest, ClearClipRectsRecursiveChild) {
+  setBodyInnerHTML(
+      "<style>"
+      "div { "
+      "  width: 5px; height: 5px; background: blue;"
+      "  position: relative;"
+      "}"
+      "</style>"
+      "<div id='parent'>"
+      "  <div id='child'>"
+      "    <div id='grandchild'></div>"
+      "  </div>"
+      "</div>");
+
+  PaintLayer* parent =
+      toLayoutBoxModelObject(getLayoutObjectByElementId("parent"))->layer();
+  PaintLayer* child =
+      toLayoutBoxModelObject(getLayoutObjectByElementId("child"))->layer();
+
+  EXPECT_TRUE(parent->clipRectsCache());
+  EXPECT_TRUE(child->clipRectsCache());
+
+  child->clipper().clearClipRectsIncludingDescendants();
+
+  EXPECT_TRUE(parent->clipRectsCache());
+  EXPECT_FALSE(child->clipRectsCache());
+}
+
+TEST_F(PaintLayerClipperTest, ClearClipRectsRecursiveOneType) {
+  setBodyInnerHTML(
+      "<style>"
+      "div { "
+      "  width: 5px; height: 5px; background: blue;"
+      "  position: relative;"
+      "}"
+      "</style>"
+      "<div id='parent'>"
+      "  <div id='child'>"
+      "    <div id='grandchild'></div>"
+      "  </div>"
+      "</div>");
+
+  PaintLayer* parent =
+      toLayoutBoxModelObject(getLayoutObjectByElementId("parent"))->layer();
+  PaintLayer* child =
+      toLayoutBoxModelObject(getLayoutObjectByElementId("child"))->layer();
+
+  EXPECT_TRUE(parent->clipRectsCache());
+  EXPECT_TRUE(child->clipRectsCache());
+  EXPECT_TRUE(parent->clipRectsCache()->get(AbsoluteClipRects).root);
+  EXPECT_TRUE(child->clipRectsCache()->get(AbsoluteClipRects).root);
+
+  parent->clipper().clearClipRectsIncludingDescendants(AbsoluteClipRects);
+
+  EXPECT_TRUE(parent->clipRectsCache());
+  EXPECT_TRUE(child->clipRectsCache());
+  EXPECT_FALSE(parent->clipRectsCache()->get(AbsoluteClipRects).root);
+  EXPECT_FALSE(parent->clipRectsCache()->get(AbsoluteClipRects).root);
+}
+
 }  // namespace blink