Slimming Paint phase 2 compositing algorithm plumbing

Source/core/frame/FrameView.cpp

Index: Source/core/frame/FrameView.cpp
diff --git a/Source/core/frame/FrameView.cpp b/Source/core/frame/FrameView.cpp
index 0db15c40762f84fa5451a111e168b3d83a401395..92aa2a82c1e4ec7c7de5c27508221abf0020251f 100644
--- a/Source/core/frame/FrameView.cpp
+++ b/Source/core/frame/FrameView.cpp
@@ -29,6 +29,7 @@
 
 #include "core/HTMLNames.h"
 #include "core/MediaTypeNames.h"
+#include "core/compositing/DisplayListCompositingBuilder.h"
 #include "core/css/FontFaceSet.h"
 #include "core/css/resolver/StyleResolver.h"
 #include "core/dom/AXObjectCache.h"
@@ -92,6 +93,7 @@
 #include "platform/graphics/GraphicsContext.h"
 #include "platform/graphics/GraphicsLayer.h"
 #include "platform/graphics/GraphicsLayerDebugInfo.h"
+#include "platform/graphics/paint/DisplayItemList.h"
 #include "platform/scroll/ScrollAnimator.h"
 #include "platform/text/TextStream.h"
 #include "wtf/CurrentTime.h"
@@ -2439,15 +2441,21 @@ void FrameView::updateAllLifecyclePhases()
     frame().localFrameRoot()->view()->updateAllLifecyclePhasesInternal();
 }
 
-// TODO(chrishtr): add a scrolling update lifecycle phase, after compositing and before invalidation.
+// TODO(chrishtr): add a scrolling update lifecycle phase.
 void FrameView::updateLifecycleToCompositingCleanPlusScrolling()
 {
     frame().localFrameRoot()->view()->updateStyleAndLayoutIfNeededRecursive();
     LayoutView* view = layoutView();
-    if (view)
+    if (view) {
+        // For SlimmingPaintV2, we still need this to set up the root layer(s).
         view->compositor()->updateIfNeededRecursive();
+    }
+
     scrollContentsIfNeededRecursive();
 
+    if (view && RuntimeEnabledFeatures::slimmingPaintV2Enabled())
+        paintAndComposite();
+
     ASSERT(lifecycle().state() >= DocumentLifecycle::CompositingClean);
 }
 
@@ -2465,15 +2473,47 @@ void FrameView::updateAllLifecyclePhasesInternal()
     if (view) {
         TRACE_EVENT1("devtools.timeline", "UpdateLayerTree", "data", InspectorUpdateLayerTreeEvent::data(m_frame.get()));
 
+        // For SlimmingPaintV2, we still need this to set up the root layer(s).
         view->compositor()->updateIfNeededRecursive();
         scrollContentsIfNeededRecursive();
         invalidateTreeIfNeededRecursive();
+        if (RuntimeEnabledFeatures::slimmingPaintV2Enabled())
+            paintAndComposite();
         updatePostLifecycleData();
 
         ASSERT(!view->hasPendingSelection());
     }
 
-    ASSERT(lifecycle().state() == DocumentLifecycle::PaintInvalidationClean);
+    ASSERT(lifecycle().state() == DocumentLifecycle::PaintInvalidationClean
+        || (RuntimeEnabledFeatures::slimmingPaintV2Enabled() && lifecycle().state() == DocumentLifecycle::CompositingClean));
+}
+
+void FrameView::paintAndComposite()
+{
+    ASSERT(frame() == page()->mainFrame() || (!frame().tree().parent()->isLocalFrame()));
+
+    LayoutView* view = layoutView();
+    ASSERT(view);
+
+    GraphicsLayer* rootGraphicsLayer = view->layer()->graphicsLayerBacking();
+
+    // Detached frames can have no root graphics layer.
+    if (!rootGraphicsLayer)
+        return;
+
+    // TODO: Update callers to pass in the interest rect.
+    IntRect interestRect = LayoutRect::infiniteIntRect();
+    GraphicsContext context(rootGraphicsLayer->displayItemList());
+    rootGraphicsLayer->paint(context, interestRect);
+
+    DisplayListDiff displayListDiff;
+    rootGraphicsLayer->displayItemList()->commitNewDisplayItems(&displayListDiff);
+    lifecycle().advanceTo(DocumentLifecycle::InCompositingUpdate);
+
+    DisplayListCompositingBuilder compositingBuilder(*rootGraphicsLayer->displayItemList(), displayListDiff, *rootGraphicsLayer);
+    compositingBuilder.build();
+
+    lifecycle().advanceTo(DocumentLifecycle::CompositingClean);
 }
 
 void FrameView::updatePostLifecycleData()