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.

 * {@link http://www.khronos.org/registry/gles/extensions/OES/OES_EGL_image_external.txt

 * GL_OES_EGL_image_external} 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