webkit_layout_tests: Add osmesa as data_dep.

BUILD.gn

 # Copyright (c) 2013 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.
 
 # This is the root build file for GN. GN will start processing by loading this
 # file, and recursively load all dependencies until all dependencies are either
 # resolved or known not to exist (which will cause the build to fail). So if
 # you add a new build file, there must be some path of dependencies from this
 # file to your new one or GN won't know about it.
 
@@ skipping 912 matching lines @@
   }
 
   # This target contains only a small subset of the layout tests,
   # and is useful for testing with the regular isolate mechanism.
   # To run the full layout test suite you need to use
   # :webkit_layout_tests_exparchive, above, instead.
   group("webkit_layout_tests") {
     testonly = true
     data_deps = [
       "//content/shell:content_shell",
+      "//third_party/mesa:osmesa",

[Dirk Pranke, 2017/02/23 02:59:11]

This doesn't seem right. Why would the layout tests themselves directly need
this? And isn't this already listed as a data dependency of content_shell?

       "//tools/imagediff",
     ]
 
     if (is_android) {
       data_deps += [
         "//breakpad:breakpad_unittests",
         "//breakpad:dump_syms",
         "//breakpad:microdump_stackwalk",
         "//breakpad:minidump_dump",
         "//breakpad:minidump_stackwalk",
@@ skipping 158 matching lines @@
   assert(target_name != "")  # Mark as used.
   sources = invoker.actual_sources
   assert(
       sources == invoker.actual_sources,
       "Do not use a platform name in your output directory (found \"$root_build_dir\"). http://crbug.com/548283")
 }
 
 assert_valid_out_dir("_unused") {
   actual_sources = [ "$root_build_dir/foo" ]
 }