Test that visual state callbacks do not deadlock.

content/renderer/visual_state_browsertest.cc

+// Copyright 2015 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/command_line.h"
+#include "base/run_loop.h"
+#include "content/public/browser/render_frame_host.h"
+#include "content/public/browser/web_contents.h"
+#include "content/public/common/content_switches.h"
+#include "content/public/renderer/render_view.h"
+#include "content/public/renderer/render_view_observer.h"
+#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/public/test/test_utils.h"
+#include "content/renderer/render_frame_impl.h"
+#include "content/shell/browser/shell.h"
+
+namespace content {
+
+class CommitObserver : public RenderViewObserver {
+ public:
+  CommitObserver(RenderView* render_view, const base::Closure& quit_closure)
+      : RenderViewObserver(render_view),
+        quit_closure_(quit_closure),
+        commit_count_(0) {}
+
+  void DidCommitCompositorFrame() override {
+    commit_count_++;
+    quit_closure_.Run();
+  }
+
+  int GetCommitCount() { return commit_count_; }
+
+ private:
+  base::Closure quit_closure_;
+  int commit_count_;
+};
+
+class VisualStateTest : public ContentBrowserTest {
+ public:
+  VisualStateTest() : callback_count_(0) {}
+
+  void SetUpCommandLine(base::CommandLine* command_line) override {
+    command_line->AppendSwitch(switches::kSingleProcess);
+  }
+
+  void WaitForCommit(int routing_id) {
+    scoped_refptr<MessageLoopRunner> runner = new MessageLoopRunner;
+    CommitObserver observer(GetRenderView(routing_id), runner->QuitClosure());
+    runner->Run();
+    EXPECT_EQ(1, observer.GetCommitCount());

[Sami, 2015/02/19 10:59:34]

I think if you add a DCHECK For MessageLoop::IsIdleForTesting here you should
have some protection against unknown, possibly commit-inducing work getting
queued up in the future.

[Ignacio Solla, 2015/02/19 11:53:54]

Done.

+  }
+
+  void InvokeVisualStateCallback(bool result) {
+    EXPECT_TRUE(result);
+    callback_count_++;
+  }
+
+  int GetCallbackCount() { return callback_count_; }
+
+ private:
+  RenderView* GetRenderView(int routing_id) {
+    return RenderView::FromRoutingID(routing_id);
+  }
+
+  int callback_count_;
+};
+
+// This test verifies that visual state callbacks do not deadlock. In other
+// words, the visual state callback should be received even if there are no
+// pending updates or commits.
+IN_PROC_BROWSER_TEST_F(VisualStateTest, CallbackDoesNotDeadlock) {
+  // This test relies on the fact that loading "about:blank" only requires a
+  // single commit. We first load "about:blank" and wait for this single
+  // commit. At that point we know that the page has stabilized and no
+  // further commits are expected. We then insert a visual state callback
+  // and verify that this causes an additional commit in order to deliver
+  // the callback.
+  // Unfortunately, if loading "about:blank" changes and starts requiring
+  // two commits then this test will prove nothing. We could detect this
+  // with a high level of confidence if we used a timeout, but that's
+  // discouraged (see https://codereview.chromium.org/939673002).
+  NavigateToURL(shell(), GURL("about:blank"));
+
+  // Wait for the commit corresponding to the load.
+  PostTaskToInProcessRendererAndWait(
+      base::Bind(&VisualStateTest::WaitForCommit, base::Unretained(this),
+                 shell()->web_contents()->GetRoutingID()));
+
+  // Insert a visual state callback.
+  shell()->web_contents()->GetMainFrame()->InsertVisualStateCallback(base::Bind(
+      &VisualStateTest::InvokeVisualStateCallback, base::Unretained(this)));
+
+  // Verify that the callback is invoked and a new commit completed.
+  PostTaskToInProcessRendererAndWait(
+      base::Bind(&VisualStateTest::WaitForCommit, base::Unretained(this),
+                 shell()->web_contents()->GetRoutingID()));
+  EXPECT_EQ(1, GetCallbackCount());
+}
+
+}  // namespace content