function TextureManager(gl) {
    this.registry = [];
    this._needsResample = [];

    this._activeTexture = 0;
    this._boundTexture = null;

    this._checkerboard = createCheckerboard();

    this.gl = gl;
}
Handles loading, binding, and resampling of textures for WebGLRenderer.

@class TextureManager
@constructor

@param {WebGL_Context} gl Context used to create and bind textures.

@return {undefined} undefined