Restore GC state after painting with a "reference" [url(#foo)] clip-path

Source/core/rendering/RenderLayer.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 1816 matching lines @@
     LayoutPoint offsetFromRoot;
     convertToLayerCoords(paintingInfo.rootLayer, offsetFromRoot);
 
     if (compositingState() == PaintsIntoOwnBacking)
         offsetFromRoot.move(subpixelAccumulation());
 
     LayoutRect rootRelativeBounds;
     bool rootRelativeBoundsComputed = false;
 
     // Apply clip-path to context.
-    bool hasClipPath = false;
+    GraphicsContextStateSaver clipStateSaver(*context, false);
     RenderStyle* style = renderer()->style();
     RenderSVGResourceClipper* resourceClipper = 0;
     ClipperContext clipperContext;
 
     // Clip-path, like border radius, must not be applied to the contents of a composited-scrolling container.
     // It must, however, still be applied to the mask layer, so that the compositor can properly mask the
     // scrolling contents and scrollbars.
     if (renderer()->hasClipPath() && !context->paintingDisabled() && style && (!needsCompositedScrolling() || paintFlags & PaintLayerPaintingChildClippingMaskPhase)) {
         ASSERT(style->clipPath());
         if (style->clipPath()->type() == ClipPathOperation::SHAPE) {
-            hasClipPath = true;
-            context->save();
+            clipStateSaver.save();
             ShapeClipPathOperation* clipPath = toShapeClipPathOperation(style->clipPath());
 
             if (!rootRelativeBoundsComputed) {
                 rootRelativeBounds = physicalBoundingBoxIncludingReflectionAndStackingChildren(paintingInfo.rootLayer, offsetFromRoot);
                 rootRelativeBoundsComputed = true;
             }
 
             context->clipPath(clipPath->path(rootRelativeBounds), clipPath->windRule());
         } else if (style->clipPath()->type() == ClipPathOperation::REFERENCE) {
             ReferenceClipPathOperation* referenceClipPathOperation = toReferenceClipPathOperation(style->clipPath());
             Document& document = renderer()->document();
             // FIXME: It doesn't work with forward or external SVG references (https://bugs.webkit.org/show_bug.cgi?id=90405)
             Element* element = document.getElementById(referenceClipPathOperation->fragment());
             if (isSVGClipPathElement(element) && element->renderer()) {
+                // FIXME: Saving at this point is not required in the 'mask'-
+                // case, or if the clip ends up empty.
+                clipStateSaver.save();
                 if (!rootRelativeBoundsComputed) {
                     rootRelativeBounds = physicalBoundingBoxIncludingReflectionAndStackingChildren(paintingInfo.rootLayer, offsetFromRoot);
                     rootRelativeBoundsComputed = true;
                 }
 
                 resourceClipper = toRenderSVGResourceClipper(toRenderSVGResourceContainer(element->renderer()));
                 if (!resourceClipper->applyClippingToContext(renderer(), rootRelativeBounds,
                     paintingInfo.paintDirtyRect, context, clipperContext)) {
                     // No need to post-apply the clipper if this failed.
                     resourceClipper = 0;
@@ skipping 128 matching lines @@
 
     // End our transparency layer
     if ((haveTransparency || paintsWithBlendMode() || createTransparencyLayerForBlendMode) && m_usedTransparency && !(m_reflectionInfo && m_reflectionInfo->isPaintingInsideReflection())) {
         context->endLayer();
         context->restore();
         m_usedTransparency = false;
     }
 
     if (resourceClipper)
         resourceClipper->postApplyStatefulResource(renderer(), context, clipperContext);
-
-    if (hasClipPath)
-        context->restore();
 }
 
 void RenderLayer::paintLayerByApplyingTransform(GraphicsContext* context, const LayerPaintingInfo& paintingInfo, PaintLayerFlags paintFlags, const LayoutPoint& translationOffset)
 {
     // This involves subtracting out the position of the layer in our current coordinate space, but preserving
     // the accumulated error for sub-pixel layout.
     LayoutPoint delta;
     convertToLayerCoords(paintingInfo.rootLayer, delta);
     delta.moveBy(translationOffset);
     TransformationMatrix transform(renderableTransform(paintingInfo.paintBehavior));
@@ skipping 1761 matching lines @@
     }
 }
 
 void showLayerTree(const WebCore::RenderObject* renderer)
 {
     if (!renderer)
         return;
     showLayerTree(renderer->enclosingLayer());
 }
 #endif