Determine if OffscreenCanvas is paintable in different rendering contexts

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

 /*
  * Copyright (c) 2008, Google Inc. All rights reserved.
  * Copyright (C) 2009 Dirk Schulze <krit@webkit.org>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
@@ skipping 86 matching lines @@
 
 ImageBuffer::~ImageBuffer()
 {
     if (m_gpuMemoryUsage) {
         DCHECK_GT(s_globalAcceleratedImageBufferCount, 0u);
         s_globalAcceleratedImageBufferCount--;
     }
     ImageBuffer::s_globalGPUMemoryUsage -= m_gpuMemoryUsage;
 }
 
+bool ImageBuffer::canCreateImageBuffer(const IntSize& size)
+{
+    if (size.isEmpty())
+        return false;
+    CheckedNumeric<int> area = size.width();
+    area *= size.height();
+    if (!area.IsValid() || area.ValueOrDie() > kMaxCanvasArea)
+        return false;
+    if (size.width() > kMaxSkiaDim || size.height() > kMaxSkiaDim)
+        return false;
+    return true;
+}
+
 SkCanvas* ImageBuffer::canvas() const
 {
     return m_surface->canvas();
 }
 
 void ImageBuffer::disableDeferral(DisableDeferralReason reason) const
 {
     return m_surface->disableDeferral(reason);
 }
 
@@ skipping 347 matching lines @@
     ASSERT(MIMETypeRegistry::isSupportedImageMIMETypeForEncoding(mimeType));
 
     Vector<unsigned char> result;
     if (!encodeImage(mimeType, quality, &result))
         return "data:,";
 
     return "data:" + mimeType + ";base64," + base64Encode(result);
 }
 
 } // namespace blink