Add options to let mojom targets override their component deps.

mojo/public/cpp/bindings/tests/mojo_test_blink_export.h

Index: mojo/public/cpp/bindings/tests/mojo_test_blink_export.h
diff --git a/mojo/public/cpp/bindings/tests/mojo_test_blink_export.h b/mojo/public/cpp/bindings/tests/mojo_test_blink_export.h
new file mode 100644
index 0000000000000000000000000000000000000000..b3bbe27421442e7c3ed2e0fb5d4a2a20ae3aa519
--- /dev/null
+++ b/mojo/public/cpp/bindings/tests/mojo_test_blink_export.h
@@ -0,0 +1,29 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MOJO_PUBLIC_CPP_BINDINGS_TESTS_MOJO_TEST_BLINK_EXPORT_H_
+#define MOJO_PUBLIC_CPP_BINDINGS_TESTS_MOJO_TEST_BLINK_EXPORT_H_
+
+#if defined(COMPONENT_BUILD)
+#if defined(WIN32)
+
+#if defined(MOJO_TEST_BLINK_IMPLEMENTATION)
+#define MOJO_TEST_BLINK_EXPORT __declspec(dllexport)
+#else
+#define MOJO_TEST_BLINK_EXPORT __declspec(dllimport)
+#endif  // defined(MOJO_TEST_BLINK_IMPLEMENTATION)
+
+#else  // defined(WIN32)
+#if defined(MOJO_TEST_BLINK_IMPLEMENTATION)
+#define MOJO_TEST_BLINK_EXPORT __attribute__((visibility("default")))
+#else
+#define MOJO_TEST_BLINK_EXPORT
+#endif
+#endif
+
+#else  // defined(COMPONENT_BUILD)
+#define MOJO_TEST_BLINK_EXPORT
+#endif
+
+#endif  // MOJO_PUBLIC_CPP_BINDINGS_TESTS_MOJO_TEST_BLINK_EXPORT_H_