GC::saveLayer() may taint the current clip.

Source/platform/graphics/GraphicsContext.cpp

 /*
  * Copyright (C) 2003, 2004, 2005, 2006, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 168 matching lines @@
     m_canvas->restoreToCount(savedState.m_restoreCount);
 }
 
 void GraphicsContext::saveLayer(const SkRect* bounds, const SkPaint* paint, SkCanvas::SaveFlags saveFlags)
 {
     if (paintingDisabled())
         return;
 
     realizeCanvasSave(SkCanvas::kMatrixClip_SaveFlag);
 
+    // We should always save the matrix and clip to match upcoming Skia behavior.
+    ASSERT(saveFlags & SkCanvas::kMatrix_SaveFlag);
+    ASSERT(saveFlags & SkCanvas::kClip_SaveFlag);
+
     m_canvas->saveLayer(bounds, paint, saveFlags);
     if (bounds)
         m_canvas->clipRect(*bounds);
     if (m_trackOpaqueRegion)
         m_opaqueRegion.pushCanvasLayer(paint);
 }
 
 void GraphicsContext::restoreLayer()
 {
     if (paintingDisabled())
@@ skipping 249 matching lines @@
 
 void GraphicsContext::beginLayer(float opacity, CompositeOperator op, const FloatRect* bounds, ColorFilter colorFilter, ImageFilter* imageFilter)
 {
     if (paintingDisabled())
         return;
 
     // We need the "alpha" layer flag here because the base layer is opaque
     // (the surface of the page) but layers on top may have transparent parts.
     // Without explicitly setting the alpha flag, the layer will inherit the
     // opaque setting of the base and some things won't work properly.
-    SkCanvas::SaveFlags saveFlags = static_cast<SkCanvas::SaveFlags>(SkCanvas::kHasAlphaLayer_SaveFlag | SkCanvas::kFullColorLayer_SaveFlag);
+    SkCanvas::SaveFlags saveFlags = static_cast<SkCanvas::SaveFlags>(
+        SkCanvas::kMatrixClip_SaveFlag | SkCanvas::kHasAlphaLayer_SaveFlag | SkCanvas::kFullColorLayer_SaveFlag);
 
     SkPaint layerPaint;
     layerPaint.setAlpha(static_cast<unsigned char>(opacity * 255));
     layerPaint.setXfermode(WebCoreCompositeToSkiaComposite(op, m_paintState->blendMode()).get());
     layerPaint.setColorFilter(WebCoreColorFilterToSkiaColorFilter(colorFilter).get());
     layerPaint.setImageFilter(imageFilter);
 
     // Filters will adjust the clip to accomodate for filter bounds, but
     // need the kClipToLayer_SaveFlag to do so. We also save the clip here, so
     // it is restored back before the filtered layer is drawn in restore().
@@ skipping 1416 matching lines @@
 
 void GraphicsContext::didDrawTextInRect(const SkRect& textRect)
 {
     if (m_trackTextRegion) {
         TRACE_EVENT0("skia", "PlatformContextSkia::trackTextRegion");
         m_textRegion.join(textRect);
     }
 }
 
 }