Fix masking cull rects

Source/core/paint/SVGMaskPainter.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/paint/SVGMaskPainter.h"
 
 #include "core/layout/svg/LayoutSVGResourceMasker.h"
 #include "core/paint/CompositingRecorder.h"
 #include "core/paint/LayoutObjectDrawingRecorder.h"
 #include "core/paint/PaintInfo.h"
-#include "core/paint/TransformRecorder.h"
 #include "platform/graphics/paint/CompositingDisplayItem.h"
 #include "platform/graphics/paint/DisplayItemList.h"
-#include "platform/graphics/paint/DrawingDisplayItem.h"
 
 namespace blink {
 
 bool SVGMaskPainter::prepareEffect(const LayoutObject& object, GraphicsContext* context)
 {
     ASSERT(context);
     ASSERT(m_mask.style());
     ASSERT_WITH_SECURITY_IMPLICATION(!m_mask.needsLayout());
 
     m_mask.clearInvalidationMask();
@@ skipping 40 matching lines @@
     }
 }
 
 void SVGMaskPainter::drawMaskForLayoutObject(GraphicsContext* context, const LayoutObject& layoutObject, const FloatRect& targetBoundingBox)
 {
     ASSERT(context);
 
     AffineTransform contentTransformation;
     RefPtr<const SkPicture> maskContentPicture = m_mask.createContentPicture(contentTransformation, targetBoundingBox);
 
-    TransformRecorder recorder(*context, layoutObject, contentTransformation);
-
-    LayoutObjectDrawingRecorder drawingRecorder(*context, layoutObject, DisplayItem::SVGMask, LayoutRect::infiniteIntRect());

[chrishtr, 2015/06/12 16:03:03]

Curious: why did the infinite rect not work?

-    if (!drawingRecorder.canUseCachedDrawing())
+    LayoutObjectDrawingRecorder drawingRecorder(*context, layoutObject, DisplayItem::SVGMask, targetBoundingBox);

[fs, 2015/06/12 08:12:31]

targetBoundingBox could be too tight - maybe expose m_maskContentBoundaries and
use that? (Or use the paintInvalidationRect from object.)

+    if (!drawingRecorder.canUseCachedDrawing()) {

[fs, 2015/06/12 08:12:31]

Early out?

+        context->save();
+        context->concatCTM(contentTransformation);
         context->drawPicture(maskContentPicture.get());
+        context->restore();
+    }
 }
 
 }