Blimp: improve FontFetcher mojo ipc unittest

blimp/engine/mojo/font_fetcher_mojo_impl_unittest.cc

 // 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.
 
 #include "base/macros.h"
 #include "blimp/engine/browser/font_data_fetcher.h"
 #include "blimp/engine/mojo/font_fetcher_mojo_impl.h"
 #include "mojo/public/cpp/system/buffer.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ skipping 37 matching lines @@
   std::string contents(static_cast<const char*>(mapping.get()), size);
   EXPECT_EQ(kTestString, contents);
 }
 
 class FontFetcherMojoImplUnittest : public testing::Test {
  public:
   FontFetcherMojoImplUnittest()
       : font_fetcher_mojo_impl_(new FakeFontDataFetcher()) {}
   ~FontFetcherMojoImplUnittest() override {}
 
+ protected:
+  base::MessageLoop message_loop_;
   FontFetcherMojoImpl font_fetcher_mojo_impl_;
 };
 
-// TODO(mlliu): add tests later to do a full IPC test, calling the FontFetcher
-// API via the corresponding Mojo client interface.
 TEST_F(FontFetcherMojoImplUnittest, VerifyWriteToDataPipe) {
+  mojom::FontFetcherPtr mojo_ptr;
+  font_fetcher_mojo_impl_.BindRequest(GetProxy(&mojo_ptr));
+
   // Expect that dummy font data is written correctly to a Mojo DataPipe.
-  font_fetcher_mojo_impl_.GetFontStream(kFakeHash,
-                                        base::Bind(&VerifyDataWriteCorrectly));
+  mojo_ptr->GetFontStream(kFakeHash, base::Bind(&VerifyDataWriteCorrectly));
 
   // Expect empty handle if the font stream is empty.
-  font_fetcher_mojo_impl_.GetFontStream("", base::Bind(&VerifyEmptyDataWrite));
+  mojo_ptr->GetFontStream("", base::Bind(&VerifyEmptyDataWrite));
 }
 
 }  // namespace
 }  // namespace engine
 }  // namespace blimp