Reduce GPU mailbox size to 16 bytes

cc/ipc/struct_traits_unittest.cc

 // Copyright 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 "base/message_loop/message_loop.h"
 #include "cc/input/selection.h"
 #include "cc/ipc/traits_test_service.mojom.h"
 #include "cc/quads/debug_border_draw_quad.h"
 #include "cc/quads/render_pass.h"
 #include "cc/quads/render_pass_draw_quad.h"
@@ skipping 802 matching lines @@
   EXPECT_EQ(blend_mode, output_sqs.blend_mode);
   EXPECT_EQ(sorting_context_id, output_sqs.sorting_context_id);
 }
 
 TEST_F(StructTraitsTest, TransferableResource) {
   const uint32_t id = 1337;
   const ResourceFormat format = ALPHA_8;
   const uint32_t filter = 1234;
   const gfx::Size size(1234, 5678);
   const int8_t mailbox_name[GL_MAILBOX_SIZE_CHROMIUM] = {
-      0, 9, 8, 7, 6, 5, 4, 3, 2, 1, 9, 7, 5, 3, 1, 2, 4, 6, 8, 0, 0, 9,
-      8, 7, 6, 5, 4, 3, 2, 1, 9, 7, 5, 3, 1, 2, 4, 6, 8, 0, 0, 9, 8, 7,
-      6, 5, 4, 3, 2, 1, 9, 7, 5, 3, 1, 2, 4, 6, 8, 0, 0, 9, 8, 7};
+      0, 9, 8, 7, 6, 5, 4, 3, 2, 1, 9, 7, 5, 3, 1, 2};
   const gpu::CommandBufferNamespace command_buffer_namespace = gpu::IN_PROCESS;
   const int32_t extra_data_field = 0xbeefbeef;
   const gpu::CommandBufferId command_buffer_id(
       gpu::CommandBufferId::FromUnsafeValue(0xdeadbeef));
   const uint64_t release_count = 0xdeadbeefdeadL;
   const uint32_t texture_target = 1337;
   const bool read_lock_fences_enabled = true;
   const bool is_software = false;
   const bool is_overlay_candidate = true;
 
@@ skipping 82 matching lines @@
   EXPECT_EQ(u_plane_resource_id, out_quad->u_plane_resource_id());
   EXPECT_EQ(v_plane_resource_id, out_quad->v_plane_resource_id());
   EXPECT_EQ(a_plane_resource_id, out_quad->a_plane_resource_id());
   EXPECT_EQ(color_space, out_quad->color_space);
   EXPECT_EQ(resource_offset, out_quad->resource_offset);
   EXPECT_EQ(resource_multiplier, out_quad->resource_multiplier);
   EXPECT_EQ(bits_per_channel, out_quad->bits_per_channel);
 }
 
 }  // namespace cc