Refactor the way PaintArtifactCompositor is attached and used.

third_party/WebKit/Source/core/frame/FrameView.cpp

Index: third_party/WebKit/Source/core/frame/FrameView.cpp
diff --git a/third_party/WebKit/Source/core/frame/FrameView.cpp b/third_party/WebKit/Source/core/frame/FrameView.cpp
index 048e7d1c315d85fd90c25e562ffe98c1cde3a5ad..63ca3b805ac0b0ffb138b60bb1664ebd29f21c50 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.cpp
+++ b/third_party/WebKit/Source/core/frame/FrameView.cpp
@@ -106,6 +106,7 @@
 #include "platform/graphics/GraphicsContext.h"
 #include "platform/graphics/GraphicsLayer.h"
 #include "platform/graphics/GraphicsLayerDebugInfo.h"
+#include "platform/graphics/compositing/PaintArtifactCompositor.h"
 #include "platform/graphics/paint/CullRect.h"
 #include "platform/graphics/paint/PaintController.h"
 #include "platform/graphics/paint/ScopedPaintChunkProperties.h"
@@ -2762,12 +2763,20 @@ void FrameView::pushPaintArtifactToCompositor()
 
     ASSERT(RuntimeEnabledFeatures::slimmingPaintV2Enabled());
 
-    const PaintArtifact& paintArtifact = m_paintController->paintArtifact();
-
     Page* page = frame().page();
     if (!page)
         return;
-    page->chromeClient().didPaint(paintArtifact);
+
+    if (!m_paintArtifactCompositor) {
+        m_paintArtifactCompositor = PaintArtifactCompositor::create();
+        page->chromeClient().attachRootLayer(m_paintArtifactCompositor->getWebLayer(), &frame());

[jbroman, 2016/09/15 21:31:04]

For what it's worth, the concern here was that WebLayer is on the path to
eventual deprecation and core/ is not allowed to talk to cc::Layer. That was the
reason this was done in Source/web/ (though we can cross that bridge when we get
to it).

+    }
+
+    SCOPED_BLINK_UMA_HISTOGRAM_TIMER("Blink.Compositing.UpdateTime");
+
+    frameView.lifecycle().advanceTo(DocumentLifecycle::InCompositingUpdateForSlimmingPaintV2);
+    m_paintArtifactCompositor->update(m_paintController->paintArtifact());
+    frameView.lifecycle().advanceTo(DocumentLifecycle::InCompositingUpdateForSlimmingPaintV2Clean);
 }
 
 void FrameView::updateStyleAndLayoutIfNeededRecursive()