Declarative resource hints go through mojo IPC to //content

content/browser/loader/resource_hints_browsertest.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 "content/public/test/browser_test_utils.h"
+#include "content/public/test/content_browser_test.h"
+#include "content/public/test/content_browser_test_utils.h"
+#include "content/shell/browser/shell.h"
+#include "net/dns/host_resolver_proc.h"
+#include "net/dns/mock_host_resolver.h"
+#include "testing/gmock/include/gmock/gmock.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace content {
+
+using ::testing::_;
+
+class MockHostResolverProc : public net::HostResolverProc {
+ public:
+  MockHostResolverProc() : net::HostResolverProc(nullptr) {}
+
+  MOCK_METHOD5(Resolve,
+               int(const std::string& host,
+                   net::AddressFamily address_family,
+                   net::HostResolverFlags flags,
+                   net::AddressList* addresses,
+                   int* os_error));
+
+ private:
+  ~MockHostResolverProc() override {}
+};
+
+class ResourceHintsBrowserTest : public ContentBrowserTest {
+ public:
+  ResourceHintsBrowserTest()
+      : mock_host_resolver_proc_(new MockHostResolverProc),
+        scoped_host_resolver_proc_(nullptr) {}
+
+ protected:
+  scoped_refptr<MockHostResolverProc> mock_host_resolver_proc_;
+  std::unique_ptr<net::ScopedDefaultHostResolverProc>
+      scoped_host_resolver_proc_;
+};
+
+IN_PROC_BROWSER_TEST_F(ResourceHintsBrowserTest, DnsPrefetch) {
+  scoped_host_resolver_proc_.reset(
+      new net::ScopedDefaultHostResolverProc(mock_host_resolver_proc_.get()));
+  ASSERT_TRUE(embedded_test_server()->Start());
+
+  EXPECT_CALL(*mock_host_resolver_proc_, Resolve("chromium.org", _, _, _, _))

[mmenke, 2016/06/17 20:05:36]

I'd recommend against using Gmock - it reduces the amount of needed information
to start hacking on chrome, and makes for much more obscure code.

[Charlie Harrison, 2016/06/19 11:01:56]

Hm. I think I disagree with you. To extend these tests, we'll need to keep track
of a vector of calls to Resolve, with added boilerplate code to iterate through
and find out if various hosts were called.

Do you think that's a better approach? I think Gmock gets rid of a ton of
unnecessary boilerplate and makes tests much simpler to understand if they
follow a particular pattern (tracking method calls).

Happy to defer to your opinion if you feel strongly about this though.

+      .Times(1);
+  EXPECT_CALL(*mock_host_resolver_proc_,
+              Resolve(testing::Ne("chromium.org"), _, _, _, _))
+      .Times(0);
+  EXPECT_TRUE(NavigateToURL(shell(), embedded_test_server()->GetURL(
+                                         "/resource_hints/dns_prefetch.html")));
+  EXPECT_TRUE(
+      NavigateToURL(shell(), embedded_test_server()->GetURL("/title1.html")));
+  scoped_host_resolver_proc_.reset();
+}
+
+}  // namespace content