Checkpoint work to get GN builds working on Android.

tools/gn/secondary/testing/gtest/BUILD.gn

Index: tools/gn/secondary/testing/gtest/BUILD.gn
diff --git a/tools/gn/secondary/testing/gtest/BUILD.gn b/tools/gn/secondary/testing/gtest/BUILD.gn
index b77d178c14563def5271ae0b8f60f0a28f7639ce..06bfc2e74e1b4afbf4cdee66964341992f8777ad 100644
--- a/tools/gn/secondary/testing/gtest/BUILD.gn
+++ b/tools/gn/secondary/testing/gtest/BUILD.gn
@@ -30,6 +30,21 @@ config("gtest_config") {
       "GTEST_HAS_RTTI=0",
     ]
   }
+
+  if (is_android) {
+    defines += [
+      # We want gtest features that use tr1::tuple, but we currently
+      # don't support the variadic templates used by libstdc++'s
+      # implementation. gtest supports this scenario by providing its
+      # own implementation but we must opt in to it.
+      "GTEST_USE_OWN_TR1_TUPLE=1",
+           
+      # GTEST_USE_OWN_TR1_TUPLE only works if GTEST_HAS_TR1_TUPLE is set.
+      # gtest r625 made it so that GTEST_HAS_TR1_TUPLE is set to 0
+      # automatically on android, so it has to be set explicitly here.
+      "GTEST_HAS_TR1_TUPLE=1",
+    ]
+  }
 }
 
 static_library("gtest") {