Add tools for code coverage support in iOS.

build/secondary/testing/gtest/BUILD.gn

Index: build/secondary/testing/gtest/BUILD.gn
diff --git a/build/secondary/testing/gtest/BUILD.gn b/build/secondary/testing/gtest/BUILD.gn
index 649f5c559db4054f6815b77432f39e04e0ca769e..7eeceef55e28ec25ea0c1fe2213bacc673e14e9c 100644
--- a/build/secondary/testing/gtest/BUILD.gn
+++ b/build/secondary/testing/gtest/BUILD.gn
@@ -3,6 +3,10 @@
 # found in the LICENSE file.
 
 import("//build_overrides/gtest.gni")
+if (is_ios) {
+  import("//build/config/ios/ios_sdk.gni")
+  import("//build/buildflag_header.gni")
+}
 
 config("gtest_config") {
   visibility = [
@@ -72,6 +76,7 @@ static_library("gtest") {
     "src/gtest-typed-test.cc",
     "src/gtest.cc",
   ]
+  deps = []
 
   if (gtest_include_multiprocess) {
     sources += [
@@ -100,9 +105,10 @@ static_library("gtest") {
 
   if (is_ios && gtest_include_ios_coverage) {
     sources += [
-      "../coverage_util_ios.cc",
       "../coverage_util_ios.h",
+      "../coverage_util_ios.mm",
     ]
+    deps += [ ":ios_enable_coverage" ]
   }
 
   include_dirs = [ "." ]
@@ -128,3 +134,10 @@ source_set("gtest_main") {
     ":gtest",
   ]
 }
+
+if (is_ios) {
+  buildflag_header("ios_enable_coverage") {
+    header = "ios_enable_coverage.h"
+    flags = [ "IOS_ENABLE_COVERAGE=$ios_enable_coverage" ]
+  }
+}