code: function wrapInstancedArraysExtension(ctx, proto) {
      /**
       * @param {string} signature Event signature.
       * @param {Function=} opt_generator Generator function.
       */
      function wrapInstancedArraysMethod(signature, opt_generator) {
        wrapMethod(
            proto, 'ANGLEInstancedArrays',
            signature, opt_generator);
      };
  
      wrapInstancedArraysMethod(
          'drawArraysInstancedANGLE(uint32 mode, uint32 first, int32 count, ' +
              'int32 primcount)',
          function(fn, eventType) {
            return function drawArraysInstancedANGLE() {
              setCurrentContext(ctx);
              var scope = eventType.apply(this, arguments);
              return leaveScope(scope, fn.apply(this, arguments));
            };
          });
      wrapInstancedArraysMethod(
          'drawElementsInstancedANGLE(uint32 mode, int32 count, uint32 type, ' +
              'uint32 offset, int32 primcount)',
          function(fn, eventType) {
            return function drawElementsInstancedANGLE() {
              setCurrentContext(ctx);
              var scope = eventType.apply(this, arguments);
              return leaveScope(scope, fn.apply(this, arguments));
            };
          });
      wrapInstancedArraysMethod(
          'vertexAttribDivisorANGLE(uint32 index, uint32 divisor)',
          function(fn, eventType) {
            return function vertexAttribDivisorANGLE() {
              setCurrentContext(ctx);
              var scope = eventType.apply(this, arguments);
              return leaveScope(scope, fn.apply(this, arguments));
            };
          });
    }
docs: Wraps the ANGLEInstancedArrays extension object.
  @param {!WebGLRenderingContext} ctx Target context.
  @param {!Object} proto Prototype object.