[New Multicolumn] Render transformed layers into multiple fragments.

Source/core/layout/Layer.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 1534 matching lines @@
         m_scrollableArea = adoptPtr(new LayerScrollableArea(*this));
     else
         m_scrollableArea = nullptr;
 }
 
 bool Layer::hasOverflowControls() const
 {
     return m_scrollableArea && (m_scrollableArea->hasScrollbar() || m_scrollableArea->scrollCorner() || renderer()->style()->resize() != RESIZE_NONE);
 }
 
+void Layer::appendSingleFragmentIgnoringPagination(LayerFragments& fragments, const Layer* rootLayer, const LayoutRect& dirtyRect, ClipRectsCacheSlot clipRectsCacheSlot, OverlayScrollbarSizeRelevancy inOverlayScrollbarSizeRelevancy, ShouldRespectOverflowClip respectOverflowClip, const LayoutPoint* offsetFromRoot, const LayoutSize& subPixelAccumulation)
+{
+    LayerFragment fragment;
+    ClipRectsContext clipRectsContext(rootLayer, clipRectsCacheSlot, inOverlayScrollbarSizeRelevancy, subPixelAccumulation);
+    if (respectOverflowClip == IgnoreOverflowClip)
+        clipRectsContext.setIgnoreOverflowClip();
+    clipper().calculateRects(clipRectsContext, dirtyRect, fragment.layerBounds, fragment.backgroundRect, fragment.foregroundRect, fragment.outlineRect, offsetFromRoot);
+    fragments.append(fragment);
+}
+
 void Layer::collectFragments(LayerFragments& fragments, const Layer* rootLayer, const LayoutRect& dirtyRect,
     ClipRectsCacheSlot clipRectsCacheSlot, OverlayScrollbarSizeRelevancy inOverlayScrollbarSizeRelevancy, ShouldRespectOverflowClip respectOverflowClip, const LayoutPoint* offsetFromRoot,
     const LayoutSize& subPixelAccumulation, const LayoutRect* layerBoundingBox)
 {
-    if (!enclosingPaginationLayer() || hasTransformRelatedProperty()) {
+    if (!enclosingPaginationLayer()) {
         // For unpaginated layers, there is only one fragment.
-        LayerFragment fragment;
-        ClipRectsContext clipRectsContext(rootLayer, clipRectsCacheSlot, inOverlayScrollbarSizeRelevancy, subPixelAccumulation);
-        if (respectOverflowClip == IgnoreOverflowClip)
-            clipRectsContext.setIgnoreOverflowClip();
-        clipper().calculateRects(clipRectsContext, dirtyRect, fragment.layerBounds, fragment.backgroundRect, fragment.foregroundRect, fragment.outlineRect, offsetFromRoot);
-        fragments.append(fragment);
+        appendSingleFragmentIgnoringPagination(fragments, rootLayer, dirtyRect, clipRectsCacheSlot, inOverlayScrollbarSizeRelevancy, respectOverflowClip, offsetFromRoot, subPixelAccumulation);
         return;
     }
 
     // Compute our offset within the enclosing pagination layer.
     LayoutPoint offsetWithinPaginatedLayer;
     convertToLayerCoords(enclosingPaginationLayer(), offsetWithinPaginatedLayer);
 
     // Calculate clip rects relative to the enclosingPaginationLayer. The purpose of this call is to determine our bounds clipped to intermediate
     // layers between us and the pagination context. It's important to minimize the number of fragments we need to create and this helps with that.
     ClipRectsContext paginationClipRectsContext(enclosingPaginationLayer(), clipRectsCacheSlot, inOverlayScrollbarSizeRelevancy);
@@ skipping 300 matching lines @@
     hitLayer = hitTestChildren(NormalFlowChildren, rootLayer, request, result, hitTestRect, hitTestLocation,
         localTransformState.get(), zOffsetForDescendantsPtr, zOffset, unflattenedTransformState.get(), depthSortDescendants);
     if (hitLayer) {
         if (!depthSortDescendants)
             return hitLayer;
         candidateLayer = hitLayer;
     }
 
     // Collect the fragments. This will compute the clip rectangles for each layer fragment.
     LayerFragments layerFragments;
-    collectFragments(layerFragments, rootLayer, hitTestRect, RootRelativeClipRects, IncludeOverlayScrollbarSize);
+    if (appliedTransform)
+        appendSingleFragmentIgnoringPagination(layerFragments, rootLayer, hitTestRect, RootRelativeClipRects, IncludeOverlayScrollbarSize);
+    else
+        collectFragments(layerFragments, rootLayer, hitTestRect, RootRelativeClipRects, IncludeOverlayScrollbarSize);
 
     if (m_scrollableArea && m_scrollableArea->hitTestResizerInFragments(layerFragments, hitTestLocation)) {
         renderer()->updateHitTestResult(result, hitTestLocation.point());
         return this;
     }
 
     // Next we want to see if the mouse pos is inside the child LayoutObjects of the layer. Check
     // every fragment in reverse order.
     if (isSelfPaintingLayer()) {
         // Hit test with a temporary HitTestResult, because we only want to commit to 'result' if we know we're frontmost.
@@ skipping 1038 matching lines @@
     }
 }
 
 void showLayerTree(const blink::LayoutObject* renderer)
 {
     if (!renderer)
         return;
     showLayerTree(renderer->enclosingLayer());
 }
 #endif