Incorrect LocalFrame::paintIntoDragImage picture bounds

Source/core/frame/LocalFrame.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Simon Hausmann <hausmann@kde.org>
  *                     2000 Stefan Schimanski <1Stein@gmx.de>
  *                     2001 George Staikos <staikos@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2005 Alexey Proskuryakov <ap@nypop.com>
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
@@ skipping 580 matching lines @@
     const GlobalPaintFlags globalPaintFlags, IntRect paintingRect, float opacity)
 {
     ASSERT(document()->isActive());
     // Not flattening compositing layers will result in a broken image being painted.
     ASSERT(globalPaintFlags & GlobalPaintFlattenCompositingLayers);
 
     float deviceScaleFactor = m_host->deviceScaleFactor();
     paintingRect.setWidth(paintingRect.width() * deviceScaleFactor);
     paintingRect.setHeight(paintingRect.height() * deviceScaleFactor);
 
-    SkPictureBuilder pictureBuilder(paintingRect);
+    SkPictureBuilder pictureBuilder(FloatRect(FloatPoint(), paintingRect.size()));

[mtklein_C, 2015/08/18 14:07:06]

Think it's worth adding a note similar to the CL description here?  Or is this
obvious in retrospect?

[f(malita), 2015/08/18 17:40:14]

Done.

     {
         GraphicsContext& paintContext = pictureBuilder.context();
 
         AffineTransform transform;
         transform.scale(deviceScaleFactor, deviceScaleFactor);
         transform.translate(-paintingRect.x(), -paintingRect.y());

[Justin Novosad, 2015/08/18 14:36:33]

I suppose this is the transaction to counteract the origin shift? What use case
exactly was broken before this change? Could you add a BUG= to the description?

[f(malita), 2015/08/18 17:40:14]

We're ultimately drawing this into a (0,0) - (paintingRect.width(),
paintingRect.height()) bitmap, so this is just mapping the content rect to the
bitmap bounds.

The problem is we're not doing the same for the SKP cull rect - so while we're
drawing near origin, the SKP thinks its content is some place else.

Nothing is broken currently, because the SKP cull rect is only used for
quick-reject by the BBH (and these drag images are not recorded within the
normal SKP hierarchy).

But it blocks http://crrev.com/1264133003 which generalizes the quick reject at
the SkCanvas level.  With that in place, the dragImage SKP bounds need to be
correct to avoid spurious culling.

Added a BUG.

         TransformRecorder transformRecorder(paintContext, displayItemClient, transform);
 
         m_view->paintContents(&paintContext, globalPaintFlags, paintingRect);
 
     }
     RefPtr<const SkPicture> recording = pictureBuilder.endRecording();
     RefPtr<SkImage> skImage = adoptRef(SkImage::NewFromPicture(recording.get(),
         SkISize::Make(paintingRect.width(), paintingRect.height()), nullptr, nullptr));
     RefPtr<Image> image = StaticBitmapImage::create(skImage.release());
 
@@ skipping 226 matching lines @@
 {
     if (isLocalRoot())
         m_instrumentingAgents = InstrumentingAgents::create();
     else
         m_instrumentingAgents = localFrameRoot()->m_instrumentingAgents;
 }
 
 DEFINE_WEAK_IDENTIFIER_MAP(LocalFrame);
 
 } // namespace blink