Fix Slimming Paint WebGL printing

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 1079 matching lines @@
 
     m_canvas->writePixels(info, pixels, rowBytes, x, y);
 }
 
 void GraphicsContext::drawBitmapRect(const SkBitmap& bitmap, const SkRect* src,
     const SkRect& dst, const SkPaint* paint)
 {
     // Textures are bound to the blink main-thread GrContext, which can not be
     // used on the compositor raster thread.
     // FIXME: Mailbox support would make this possible in the GPU-raster case.
-    ASSERT(!isRecording() || !bitmap.getTexture());
+    // If we're printing it is safe to access the texture because we are always
+    // on main thread, even if the other conditions are not met.
+    ASSERT(!isRecording() || !bitmap.getTexture() || printing());

[chrishtr, 2015/05/20 18:20:40]

I assume that when slimming paint is off, and printing is on, the code that
generates an SkBitmap and passes it to drawBitmapRect always does so without a
texture. Is that right?

And if so, it seems we should have the same sort of logic with slimming paint.
Maybe the SkBitmap-creation logic checks for isRecording(), and we should check
for isRecording() || printing()?

[Stephen Chennney, 2015/05/20 18:30:13]

There is a texture during printing, probably because it's WebGL and there needs
to be a texture to capture the content. I'll look further into where this
texture comes from.
I'll look.

It is the case that the thing the assert is checking for, use of a texture off
the Blink main thread, is not a problem when printing. So on some fundamental
level the assert is too aggressive.

     if (contextDisabled())
         return;
 
     SkCanvas::DrawBitmapRectFlags flags =
         immutableState()->shouldClampToSourceRect() ? SkCanvas::kNone_DrawBitmapRectFlag : SkCanvas::kBleed_DrawBitmapRectFlag;
 
     ASSERT(m_canvas);
     m_canvas->drawBitmapRectToRect(bitmap, src, dst, paint, flags);
 }
 
@@ skipping 659 matching lines @@
         // being returned from computeInterpolationQuality.
         resampling = InterpolationLow;
     }
     resampling = limitInterpolationQuality(this, resampling);
     paint->setFilterQuality(static_cast<SkFilterQuality>(resampling));
 
     return initialSaveCount;
 }
 
 } // namespace blink