Bug 222410

RemoteGraphicsContext ReadPixels does not preserve contents for area that is not written When readPixels is used with source rectangle that contains areas that are not part of the Framebuffer, then the memory contents of the buffer should not be changed for that part. E.g. when doing data[0] = 77; readPixels(-1, -1, 10000000, 10000000, .., data) then data[0] should be preserved as 77 as -1,-1 is not part of the framebuffer being read. Problem since the webp->gpup does not don't transfer the buffer, but also does not risk the calculations to only populate part of the result buffer. webgl/2.0.0/conformance/reading/read-pixels-test.html [ Failure ] webgl/2.0.0/conformance2/reading/read-pixels-pack-parameters.html [ Failure ]