Have compositor_model_bench target near its source files.

It is more traditional (and recommended) to have GN targets closer to the source
files it builds.

BUG=432959
TEST=gn gen out-gn && ninja -C out-gn compositor_model_bench
R=sievers@chromium.org, dpranke@chromium.org

Review URL: https://codereview.chromium.org/1032193002

Cr-Commit-Position: refs/heads/master@{#322226}

BUILD.gn

@@ -375,7 +375,7 @@ group("gn_all") {
     if (use_x11) {
       deps += [ "//media:player_x11" ]
       if (target_cpu != "arm") {
-        deps += [ "//gpu:compositor_model_bench" ]
+        deps += [ "//gpu/tools/compositor_model_bench" ]
       }
     }
   }

gpu/BUILD.gn

@@ -291,25 +291,3 @@ test("angle_unittests") {
     "//third_party/angle:translator_static",
   ]
 }
-
-if (is_linux && !is_chromeos && target_cpu != "arm" && use_x11) {
-  executable("compositor_model_bench") {
-    sources = [
-      "tools/compositor_model_bench/compositor_model_bench.cc",
-      "tools/compositor_model_bench/forward_render_model.cc",
-      "tools/compositor_model_bench/render_model_utils.cc",
-      "tools/compositor_model_bench/render_models.cc",
-      "tools/compositor_model_bench/render_tree.cc",
-      "tools/compositor_model_bench/shaders.cc",
-    ]
-
-    libs = [ "GL" ]
-
-    configs += [ "//build/config/linux:x11" ]
-
-    deps = [
-      "//base",
-      "//ui/gl",
-    ]
-  }
-}

gpu/tools/compositor_model_bench/BUILD.gn

+# Copyright 2015 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.
+
+import("//build/config/ui.gni")
+
+if (is_linux && !is_chromeos && target_cpu != "arm" && use_x11) {
+  # GYP version: //gpu/tools/tools.gyp:compositor_model_bench
+  executable("compositor_model_bench") {
+    sources = [
+      "compositor_model_bench.cc",
+      "forward_render_model.cc",
+      "render_model_utils.cc",
+      "render_models.cc",
+      "render_tree.cc",
+      "shaders.cc",
+    ]
+
+    libs = [ "GL" ]
+
+    configs += [ "//build/config/linux:x11" ]
+
+    deps = [
+      "//base",
+      "//ui/gl",
+    ]
+  }
+}

gpu/tools/tools.gyp

@@ -12,7 +12,7 @@
     ['OS == "linux" and target_arch != "arm" and use_x11==1', {
       'targets': [
         {
-          # GN: //gpu:compositor_model_bench
+          # GN version: //gpu/tools/compositor_model_bench
           'target_name': 'compositor_model_bench',
           'type': 'executable',
           'dependencies': [