Merge "Expand on the SurfaceTexture API docs."

 * be done by transforming (1, 1, 0, 1).

 *

 * <p>The texture object uses the GL_TEXTURE_EXTERNAL_OES texture target, which is defined by the

 * OES_EGL_image_external OpenGL ES extension.  This limits how the texture may be used.

 * <a href="http://www.khronos.org/registry/gles/extensions/OES/OES_EGL_image_external.txt">

 * GL_OES_EGL_image_external</a> OpenGL ES extension.  This limits how the texture may be used.

 * Each time the texture is bound it must be bound to the GL_TEXTURE_EXTERNAL_OES target rather than

 * the GL_TEXTURE_2D target.  Additionally, any OpenGL ES 2.0 shader that samples from the texture

 * must declare its use of this extension using, for example, an "#extension

 * GL_OES_EGL_image_external : require" directive.  Such shaders must also access the texture using

 * the samplerExternalOES GLSL sampler type.

 *

 * <p>SurfaceTexture objects may be created on any thread.  {@link #updateTexImage} may only be

 * called on the thread with the OpenGL ES context that contains the texture object.  The