wm: Add two pass rendering to OpenGL|ES backend.

gles/real_gles2_interface.cc

 // Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "window_manager/gles/real_gles2_interface.h"
 
 #ifndef EGLAPI
 #define EGLAPI
 #endif
 
@@ skipping 231 matching lines @@
 void RealGles2Interface::DeleteShader(GLuint shader) {
   glDeleteShader(shader);
   GLES2_DCHECK_ERROR();
 }
 
 void RealGles2Interface::DeleteTextures(GLsizei n, const GLuint* textures) {
   glDeleteTextures(n, textures);
   GLES2_DCHECK_ERROR();
 }
 
+void RealGles2Interface::DepthMask(GLboolean flag) {
+  glDepthMask(flag);
+  GLES2_DCHECK_ERROR();
+}
+
 void RealGles2Interface::Disable(GLenum cap) {
   glDisable(cap);
   GLES2_DCHECK_ERROR();
 }
 
 void RealGles2Interface::DisableVertexAttribArray(GLuint index) {
   glDisableVertexAttribArray(index);
   GLES2_DCHECK_ERROR();
 }
 
@@ skipping 253 matching lines @@
 }
 
 void RealGles2Interface::EGLImageTargetRenderbufferStorageOES(
     GLenum target, GLeglImageOES image) {
   DCHECK(gl_egl_image_target_renderbuffer_storage_oes_);
   gl_egl_image_target_renderbuffer_storage_oes_(target, image);
   GLES2_DCHECK_ERROR();
 }
 
 }  // namespace window_manager