Handle shader construction failures gracefully

third_party/WebKit/Source/platform/graphics/Image.cpp

 /*
  * Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2004, 2005, 2006 Apple Computer, 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 285 matching lines @@
     return;
 
   const FloatSize tileSize(
       image->width() * scale.width() + repeatSpacing.width(),
       image->height() * scale.height() + repeatSpacing.height());
   const auto tmx = computeTileMode(destRect.x(), destRect.maxX(), adjustedX,
                                    adjustedX + tileSize.width());
   const auto tmy = computeTileMode(destRect.y(), destRect.maxY(), adjustedY,
                                    adjustedY + tileSize.height());
 
-  {
-    PaintFlags paint = context.fillPaint();
-    paint.setColor(SK_ColorBLACK);
-    paint.setBlendMode(compositeOp);
-    paint.setFilterQuality(
-        context.computeFilterQuality(this, destRect, normSrcRect));
-    paint.setAntiAlias(context.shouldAntialias());
-    paint.setShader(
-        createPatternShader(image.get(), localMatrix, paint,
-                            FloatSize(repeatSpacing.width() / scale.width(),
-                                      repeatSpacing.height() / scale.height()),
-                            tmx, tmy));
-    context.drawRect(destRect, paint);
-  }
+  PaintFlags paint = context.fillPaint();
+  paint.setColor(SK_ColorBLACK);
+  paint.setBlendMode(compositeOp);
+  paint.setFilterQuality(
+      context.computeFilterQuality(this, destRect, normSrcRect));
+  paint.setAntiAlias(context.shouldAntialias());
+  paint.setShader(
+      createPatternShader(image.get(), localMatrix, paint,
+                          FloatSize(repeatSpacing.width() / scale.width(),
+                                    repeatSpacing.height() / scale.height()),
+                          tmx, tmy));
+  // If the shader could not be instantiated (e.g. non-invertible matrix),
+  // draw transparent.
+  // Note: we can't simply bail, because of arbitrary blend mode.
+  if (!paint.getShader())
+    paint.setColor(SK_ColorTRANSPARENT);
+
+  context.drawRect(destRect, paint);
 
   if (currentFrameIsLazyDecoded())
     PlatformInstrumentation::didDrawLazyPixelRef(imageID);
 }
 
 PassRefPtr<Image> Image::imageForDefaultFrame() {
   RefPtr<Image> image(this);
 
   return image.release();
 }
 
 bool Image::applyShader(SkPaint& paint,
                         const SkMatrix& localMatrix,
                         const ColorBehavior& colorBehavior) {
   // Default shader impl: attempt to build a shader based on the current frame
   // SkImage.
   sk_sp<SkImage> image = imageForCurrentFrame(colorBehavior);
   if (!image)
     return false;
 
   paint.setShader(image->makeShader(SkShader::kRepeat_TileMode,
                                     SkShader::kRepeat_TileMode, &localMatrix));
+  if (!paint.getShader())
+    return false;
 
   // Animation is normally refreshed in draw() impls, which we don't call when
   // painting via shaders.
   startAnimation();
 
   return true;
 }
 
 FloatRect Image::computeTileContaining(const FloatPoint& point,
                                        const FloatSize& tileSize,
@@ skipping 22 matching lines @@
   FloatRect subset = dest;
   subset.setX((dest.x() - tile.x()) / scale.width());
   subset.setY((dest.y() - tile.y()) / scale.height());
   subset.setWidth(dest.width() / scale.width());
   subset.setHeight(dest.height() / scale.height());
 
   return subset;
 }
 
 }  // namespace blink