I have it on the best of authority (Maurice Ribble who works on the driver) that the Adreno 220 does not support rendering to FP buffers. As for the Tegra I see the words on page 5 however the list of extensions does not list any that would enable this functionality. The most likely suspect for this, GL_NV_fbo_color_attachments, only mentions half-float.
As others have said, OES_texture_float is not the place to enable this functionality. Another extension is needed but I do not think there is enough commonality in behaviour across implementations for sch an extension to be viable for WebGL at present.
On 2011/08/31 15:37, David Sheets wrote:Page 5 of the NVidia Tegra GL ES 2 docs <http://developer.download.nvidia.com/tegra/docs/tegra_gles2_development.pdf> indicates FP texture write support (and MRT fwiw). Adreno 220 series can do deferred lighting and cloth sim which would also seem to indicate FP texture write support.