This is an initial Blimp integration test that exercises navigation history....

This is an initial Blimp integration test that exercises navigation history. The purpose is to test the integration with WebContentsImpl and NavigationControllerImpl, as well as the proper flow of Blimp's NavigationStateChangeMessage protobuf across the client-engine network connection.

The test visits two different web pages and then goes back to the first one.

Additional supporting changes:
* Moving some setup code from the initial LoadUrl test into SetUpOnMainThread.
* Helper method ExpectPageLoad, which sets mock expectations for a page load, and can be used with the helper method RunAndVerify to wait for Blimp to load a page.
* Always storing the latest page title when it changes on the client side, making it easier to assert about what page was most recently loaded.

Review-Url: https://codereview.chromium.org/2272513003
Cr-Commit-Position: refs/heads/master@{#414755}

blimp/engine/browser_tests/engine_browsertest.cc

@@ -48,40 +48,88 @@ class EngineBrowserTest : public BlimpBrowserTest {
         kDummyTabId, &client_rw_feature_delegate_);
     client_session_->GetImeFeature()->set_delegate(
         &client_ime_feature_delegate_);
+
+    // Skip assigner. Engine info is already available.
+    client_session_->ConnectWithAssignment(client::ASSIGNMENT_REQUEST_RESULT_OK,
+                                           GetAssignment());
+    client_session_->GetTabControlFeature()->SetSizeAndScale(
+        gfx::Size(100, 100), 1);
+    client_session_->GetTabControlFeature()->CreateTab(kDummyTabId);
+
+    // Record the last page title known to the client. Page loads will sometimes
+    // involve multiple title changes in transition, including the requested
+    // URL. When a page is done loading, the last title should be the one from
+    // the <title> tag.
+    ON_CALL(client_nav_feature_delegate_,
+            OnTitleChanged(kDummyTabId, testing::_))
+        .WillByDefault(testing::SaveArg<1>(&last_page_title_));
+
+    EXPECT_TRUE(embedded_test_server()->Start());
+  }
+
+  // Given a path on the embedded local server, tell the client to navigate to
+  // that page by URL.
+  void NavigateToLocalUrl(const std::string& path) {
+    GURL url = embedded_test_server()->GetURL(path);
+    client_session_->GetNavigationFeature()->NavigateToUrlText(kDummyTabId,
+                                                               url.spec());
+  }
+
+  // Set mock expectations that a page will load. A page has loaded when the
+  // page load status changes to true, and then to false.
+  void ExpectPageLoad() {
+    testing::InSequence s;
+
+    // There may be redundant events indicating the page load status is true,
+    // so allow more than one.
+    EXPECT_CALL(client_nav_feature_delegate_,
+                OnLoadingChanged(kDummyTabId, true))
+        .Times(testing::AtLeast(1));
+    EXPECT_CALL(client_nav_feature_delegate_,
+                OnLoadingChanged(kDummyTabId, false))
+        .WillOnce(
+            InvokeWithoutArgs(this, &EngineBrowserTest::SignalCompletion));
+  }
+
+  void RunAndVerify() {
+    RunUntilCompletion();
+    testing::Mock::VerifyAndClearExpectations(&client_rw_feature_delegate_);
+    testing::Mock::VerifyAndClearExpectations(&client_nav_feature_delegate_);
   }
 
   client::MockNavigationFeatureDelegate client_nav_feature_delegate_;
   client::MockRenderWidgetFeatureDelegate client_rw_feature_delegate_;
   client::MockImeFeatureDelegate client_ime_feature_delegate_;
   std::unique_ptr<client::TestClientSession> client_session_;
+  std::string last_page_title_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(EngineBrowserTest);
 };
 
 IN_PROC_BROWSER_TEST_F(EngineBrowserTest, LoadUrl) {
-  testing::InSequence s;
-
-  EXPECT_TRUE(embedded_test_server()->Start());
-  GURL url = embedded_test_server()->GetURL("/hello.html");
-
   EXPECT_CALL(client_rw_feature_delegate_, OnRenderWidgetCreated(1));
-  EXPECT_CALL(client_nav_feature_delegate_,
-              OnTitleChanged(kDummyTabId, url.GetContent()));
-  EXPECT_CALL(client_nav_feature_delegate_,
-              OnTitleChanged(kDummyTabId, "hello"))
-      .WillOnce(InvokeWithoutArgs(this, &EngineBrowserTest::SignalCompletion));
-
-  // Skip assigner. Engine info is already available.
-  client_session_->ConnectWithAssignment(client::ASSIGNMENT_REQUEST_RESULT_OK,
-                                         GetAssignment());
-  client_session_->GetTabControlFeature()->SetSizeAndScale(gfx::Size(100, 100),
-                                                           1);
-  client_session_->GetTabControlFeature()->CreateTab(kDummyTabId);
-  client_session_->GetNavigationFeature()->NavigateToUrlText(kDummyTabId,
-                                                             url.spec());
-
-  RunUntilCompletion();
+  ExpectPageLoad();
+  NavigateToLocalUrl("/page1.html");
+  RunAndVerify();
+  EXPECT_EQ("page1", last_page_title_);
+}
+
+IN_PROC_BROWSER_TEST_F(EngineBrowserTest, GoBack) {
+  ExpectPageLoad();
+  NavigateToLocalUrl("/page1.html");
+  RunAndVerify();
+  EXPECT_EQ("page1", last_page_title_);
+
+  ExpectPageLoad();
+  NavigateToLocalUrl("/page2.html");
+  RunAndVerify();
+  EXPECT_EQ("page2", last_page_title_);
+
+  ExpectPageLoad();
+  client_session_->GetNavigationFeature()->GoBack(kDummyTabId);
+  RunAndVerify();
+  EXPECT_EQ("page1", last_page_title_);
 }
 
 }  // namespace

blimp/test/data/hello.html

-<!doctype html>
-<title>hello</title>
-<h1>Hello world!</h1>

blimp/test/data/page1.html

+<!doctype html>
+<title>page1</title>

blimp/test/data/page2.html

+<!doctype html>
+<title>page2</title>