Roll googletest to 1.8.0.

testing/gtest/BUILD.gn

+import("//build_overrides/gtest.gni")
+
+config("gtest_direct_config") {
+  visibility = [ ":*" ]
+  defines = [ "UNIT_TEST" ]
+}
+
+static_library("gtest") {
+  testonly = true
+  sources = [
+    "include/gtest/gtest-death-test.h",
+    "include/gtest/gtest-message.h",
+    "include/gtest/gtest-param-test.h",
+    "include/gtest/gtest-spi.h",
+    "include/gtest/gtest.h",
+    "include/gtest/gtest_prod.h",
+  ]
+  deps = [
+    "//third_party/googletest:gtest",
+  ]
+
+  public_configs = [ ":gtest_direct_config" ]
+
+  if (gtest_include_multiprocess) {
+    sources += [
+      "../multiprocess_func_list.cc",
+      "../multiprocess_func_list.h",
+    ]
+  }
+
+  if (gtest_include_platform_test) {
+    sources += [ "../platform_test.h" ]
+  }
+
+  if ((is_mac || is_ios) && gtest_include_objc_support) {
+    if (is_ios) {
+      set_sources_assignment_filter([])
+    }
+    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) {
+    sources += [
+      "../coverage_util_ios.cc",
+      "../coverage_util_ios.h",
+    ]
+  }
+}
+
+source_set("gtest_main") {
+  testonly = true
+  deps = [
+    "//third_party/googletest:gtest_main",
+  ]
+}