WIP: Code coverage with gcov

ios/showcase/BUILD.gn

Index: ios/showcase/BUILD.gn
diff --git a/ios/showcase/BUILD.gn b/ios/showcase/BUILD.gn
index ade3d342e3c9f8c2650ae633b616e2da51015dda..94be012a179dbb928737e7feaf26536a567f1607 100644
--- a/ios/showcase/BUILD.gn
+++ b/ios/showcase/BUILD.gn
@@ -19,6 +19,7 @@ ios_app_bundle("showcase") {
     # asan mode (this target will be empty in other cases).
     "//build/config/sanitizers:deps",
   ]
+  ldflags = [ "-fprofile-arcs" ]
   bundle_deps = [ ":launchscreen_storyboard" ]
   assert_no_deps = ios_assert_no_deps
 }
@@ -56,6 +57,7 @@ ios_eg_test("ios_showcase_egtests") {
     # asan mode (this target will be empty in other cases).
     "//build/config/sanitizers:deps",
   ]
+  ldflags = [ "-fprofile-arcs" ]
   bundle_deps = [ ":launchscreen_storyboard" ]
   assert_no_deps = ios_assert_no_deps
 }