fix --show-composited-layer-borders on Mac

gpu/command_buffer/service/gles2_cmd_decoder_passthrough_handlers.cc

 // Copyright (c) 2016 The Chromium 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 "gpu/command_buffer/service/gles2_cmd_decoder_passthrough.h"
 
 namespace gpu {
 namespace gles2 {
 
 // Custom Handlers
@@ skipping 2586 matching lines @@
   GLenum format = static_cast<GLenum>(c.format);
   GLsizei image_size = static_cast<GLsizei>(c.imageSize);
   // TODO(geofflang): Handle PIXEL_UNPACK_BUFFER case.
   const void* data = GetSharedMemoryAs<const void*>(
       c.data_shm_id, c.data_shm_offset, image_size);
   return DoCompressedTexSubImage3D(
       target, level, xoffset, yoffset, zoffset, width, height, depth,
       format, image_size, data);
 }
 
+error::Error GLES2DecoderPassthroughImpl::HandleLineWidth(
+    uint32_t immediate_data_size,
+    const volatile void* cmd_data) {
+  const volatile gles2::cmds::LineWidth& c =
+      *static_cast<const volatile gles2::cmds::LineWidth*>(cmd_data);
+  GLfloat width = static_cast<GLfloat>(c.width);
+  error::Error error = DoLineWidth(width);
+  if (error != error::kNoError) {
+    return error;
+  }
+  return error::kNoError;
+}
+
 }  // namespace gles2
 }  // namespace gpu