Fix layering violations in LengthFunctions.*, move the files into libPlatform on the GTK port.
Fix the layering-violating usages of ImageData.
Fix layering-violating usages of ContentSecurityPolicy.
Clean up DragImage.
Use Checked<uint32_t, RecordOverflow> instead of CheckedInt<uint32_t>.
Remove unnecessary includes in GraphicsContext3D.cpp, GraphicsContext3DOpenGLCommon.cpp.
Remove the topDocumentURL attribute of GraphicsContext3D::Attributes.
Remove unused DrawingBuffer::paintRenderingResultsToImageData method.
Remove unnecessary header includes in FormDataBuilder.cpp.
Align the ContentDispositionType enum definition to follow the style of other defined enums.
Remove unnecessary includes in ResourceHandleSoup.cpp.
Clean up includes in Soup's ResourceRequest header and implementation files and SocketStreamHandle header.
Forward-declare the Range class in Clipboard and Frame headers.
Migration dump.