Add tools for code coverage support in iOS.

ios/showcase/BUILD.gn

 # 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.
 
 import("//build/config/ios/rules.gni")
 import("//ios/build/chrome_build.gni")
 import("//ios/build/config.gni")
 import("//ios/third_party/earl_grey/ios_eg_test.gni")
 
 ios_app_bundle("showcase") {
   info_plist = "core/Info.plist"
   extra_substitutions = [ "IOS_BUNDLE_ID_PREFIX=$ios_app_bundle_id_prefix" ]
   output_name = "Showcase"
   deps = [
     ":features",
     "//ios/showcase/core:main",
 
     # All shared libraries must have the sanitizer deps to properly link in
     # asan mode (this target will be empty in other cases).
     "//build/config/sanitizers:deps",
   ]
+  ldflags = [ "-fprofile-instr-generate" ]

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

I am not sure this is needed on the non test targets like here the Showcase app.

   bundle_deps = [ "//ios/showcase/core/resources" ]
   assert_no_deps = ios_assert_no_deps
 }
 
 group("features") {
   deps = [
     "//ios/clean/chrome/browser/ui/tools:tools_ui",
     "//ios/showcase/content_suggestions",
     "//ios/showcase/payments",
     "//ios/showcase/settings",
@@ skipping 21 matching lines @@
     # Add all eg_tests targets below.
     "//ios/showcase/content_suggestions:eg_tests",
     "//ios/showcase/core:eg_tests",
     "//ios/showcase/tab:eg_tests",
     "//ios/showcase/tab_grid:eg_tests",
 
     # All shared libraries must have the sanitizer deps to properly link in
     # asan mode (this target will be empty in other cases).
     "//build/config/sanitizers:deps",
   ]
+  ldflags = [ "-fprofile-instr-generate" ]

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

Should I instead add to ios_eg_test template and use a variable to selectively
opt-into code coverage?

   bundle_deps = [ "//ios/showcase/core/resources" ]
   assert_no_deps = ios_assert_no_deps
 }