Add tools for code coverage support in iOS.

build/secondary/testing/gtest/BUILD.gn

 # Copyright 2014 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_overrides/gtest.gni")
 
 config("gtest_config") {
   visibility = [
     ":*",
     "//testing/gmock:*",  # gmock also shares this config.
@@ skipping 80 matching lines @@
     sources += [
       "../gtest_mac.h",
       "../gtest_mac.mm",
     ]
     if (gtest_include_platform_test) {
       sources += [ "../platform_test_mac.mm" ]
     }
     set_sources_assignment_filter(sources_assignment_filter)
   }
 
   if (is_ios && gtest_include_ios_coverage) {

[lpromero, 2017/03/31 11:22:06]

"gtest_include_ios_coverage" is mentioned here, for context in a comment below.

     sources += [
-      "../coverage_util_ios.cc",
       "../coverage_util_ios.h",
+      "../coverage_util_ios.mm",
     ]
   }
 
   include_dirs = [ "." ]
 
   all_dependent_configs = [ ":gtest_config" ]
   public_configs = [ ":gtest_direct_config" ]
 
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [
     "//build/config/compiler:no_chromium_code",
 
     # Must be after no_chromium_code for warning flags to be ordered correctly.
     ":gtest_warnings",
   ]
 }
 
 source_set("gtest_main") {
   testonly = true
   sources = [
     "src/gtest_main.cc",
   ]
   deps = [
     ":gtest",
   ]
 }