Add options to let mojom targets override their component deps.

mojo/public/cpp/bindings/tests/BUILD.gn

 # Copyright 2014 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.
 
 source_set("tests") {
   testonly = true
 
   sources = [
     "array_common_test.h",
     "array_unittest.cc",
@@ skipping 35 matching lines @@
   ]
 
   deps = [
     ":mojo_public_bindings_test_utils",
     "//mojo/edk/system",
     "//mojo/public/cpp/bindings",
     "//mojo/public/cpp/system",
     "//mojo/public/cpp/test_support:test_utils",
     "//mojo/public/interfaces/bindings/tests:test_associated_interfaces",
     "//mojo/public/interfaces/bindings/tests:test_export_component",
+    "//mojo/public/interfaces/bindings/tests:test_exported_import",
     "//mojo/public/interfaces/bindings/tests:test_interfaces",
     "//mojo/public/interfaces/bindings/tests:test_interfaces_experimental",
     "//mojo/public/interfaces/bindings/tests:test_struct_traits_interfaces",
     "//testing/gtest",
   ]
 
   data = [
     "//mojo/public/interfaces/bindings/tests/data/validation/",
   ]
 
@@ skipping 19 matching lines @@
       "container_test_util.h",
       "variant_test_util.h",
       "wtf_array_unittest.cc",
       "wtf_hash_unittest.cc",
       "wtf_types_unittest.cc",
     ]
 
     deps = [
       "//mojo/public/cpp/bindings",
       "//mojo/public/cpp/system",
+      "//mojo/public/interfaces/bindings/tests:test_export_blink_component",
+      "//mojo/public/interfaces/bindings/tests:test_exported_import_blink",
       "//mojo/public/interfaces/bindings/tests:test_interfaces",
       "//mojo/public/interfaces/bindings/tests:test_interfaces_blink",
       "//mojo/public/interfaces/bindings/tests:test_wtf_types",
       "//mojo/public/interfaces/bindings/tests:test_wtf_types_blink",
       "//testing/gtest",
     ]
   }
 }
 
 source_set("struct_with_traits_impl") {
@@ skipping 33 matching lines @@
 source_set("mojo_public_bindings_test_utils") {
   sources = [
     "validation_test_input_parser.cc",
     "validation_test_input_parser.h",
   ]
 
   deps = [
     "//mojo/public/c/system",
   ]
 }