Update from https://crrev.com/317530

build/config/android/rules.gni

Index: build/config/android/rules.gni
diff --git a/build/config/android/rules.gni b/build/config/android/rules.gni
index 33dfa37e6c2a33f3a31da77494c5a227540b2976..8ca064248e268036fbc7c1bc9231cca055da7fa0 100644
--- a/build/config/android/rules.gni
+++ b/build/config/android/rules.gni
@@ -74,6 +74,12 @@ template("generate_jni") {
         rebase_path(jni_generator_jarjar_file, root_build_dir),
       ]
     }
+    if (!is_clang) {
+      # Clang builds currently fail with --native_exports_optional due to
+      # http://llvm.org/bugs/show_bug.cgi?id=22602 - only enable for gcc.
+      # http://crbug.com/442327
+      args += [ "--native_exports_optional" ]
+    }
   }
 
   config("jni_includes_${target_name}") {
@@ -184,6 +190,12 @@ template("generate_jar_jni") {
         "--includes",
         rebase_path(jni_generator_include, root_build_dir),
       ]
+      if (!is_clang) {
+        # Clang builds currently fail with --native_exports_optional due to
+        # http://llvm.org/bugs/show_bug.cgi?id=22602 - only enable for gcc.
+        # http://crbug.com/442327
+        args += [ "--native_exports_optional" ]
+      }
     }
   }
 
@@ -346,9 +358,7 @@ template("java_cpp_enum") {
 
   action("${target_name}__generate_enum") {
     # The sources aren't compiled so don't check their dependencies.
-    # TODO(brettw) uncomment after GN binary rolled pas 314974 (which added
-    # support for this value on actions).
-    #check_includes = false
+    check_includes = false
 
     sources = invoker.sources
     script = "//build/android/gyp/java_cpp_enum.py"