Wait for focus before invoking document.hasFocus().

I'm not sure whether it should be this way - maybe
waiting for the page load (WaitForPageLoad) should
imply waiting for the focus as well; but this does
fix the previously flaky test. I've clarified the
name of the test also, since all this does is to
show that the two HeadlessWebContents instances
are independently focused at the same time.

R=caseq@chromium.com, eseckler@chromium.com

Bug: 828042
Change-Id: I174863b49ae525605a6aacb8750880d02fae3246
Reviewed-on: https://chromium-review.googlesource.com/1026993Reviewed-by: Eric Seckler <eseckler@chromium.org>
Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Commit-Queue: Johannes Henkel <johannes@google.com>
Cr-Commit-Position: refs/heads/master@{#553627}

headless/lib/headless_web_contents_browsertest.cc

@@ -322,14 +322,8 @@ IN_PROC_BROWSER_TEST_F(HeadlessNoDevToolsTabSocketTest, Test) {
   RunAsynchronousTest();
 }
 
-#if defined(OS_WIN)
-// crbug.com/828042
-#define MAYBE_Focus DISABLED_Focus
-#else
-#define MAYBE_Focus Focus
-#endif
-
-IN_PROC_BROWSER_TEST_F(HeadlessWebContentsTest, MAYBE_Focus) {
+IN_PROC_BROWSER_TEST_F(HeadlessWebContentsTest,
+                       FocusOfHeadlessWebContents_IsIndependent) {
   EXPECT_TRUE(embedded_test_server()->Start());
 
   HeadlessBrowserContext* browser_context =
@@ -340,6 +334,7 @@ IN_PROC_BROWSER_TEST_F(HeadlessWebContentsTest, MAYBE_Focus) {
           .SetInitialURL(embedded_test_server()->GetURL("/hello.html"))
           .Build();
   EXPECT_TRUE(WaitForLoad(web_contents));
+  WaitForFocus(web_contents);
 
   std::unique_ptr<runtime::EvaluateResult> has_focus =
       EvaluateScript(web_contents, "document.hasFocus()");
@@ -350,6 +345,7 @@ IN_PROC_BROWSER_TEST_F(HeadlessWebContentsTest, MAYBE_Focus) {
           .SetInitialURL(embedded_test_server()->GetURL("/hello.html"))
           .Build();
   EXPECT_TRUE(WaitForLoad(web_contents2));
+  WaitForFocus(web_contents2);
 
   // Focus of different WebContents is independent.
   has_focus = EvaluateScript(web_contents, "document.hasFocus()");

headless/test/headless_browser_test.cc

@@ -15,6 +15,7 @@
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/common/url_constants.h"
+#include "content/public/test/browser_test_utils.h"
 #include "content/public/test/test_navigation_observer.h"
 #include "headless/lib/browser/headless_browser_impl.h"
 #include "headless/lib/browser/headless_web_contents_impl.h"
@@ -188,6 +189,14 @@ bool HeadlessBrowserTest::WaitForLoad(HeadlessWebContents* web_contents) {
   return observer.last_navigation_succeeded();
 }
 
+void HeadlessBrowserTest::WaitForFocus(HeadlessWebContents* web_contents) {
+  HeadlessWebContentsImpl* web_contents_impl =
+      HeadlessWebContentsImpl::From(web_contents);
+  content::FrameFocusedObserver observer(
+      web_contents_impl->web_contents()->GetMainFrame());
+  observer.Wait();
+}
+
 std::unique_ptr<runtime::EvaluateResult> HeadlessBrowserTest::EvaluateScript(
     HeadlessWebContents* web_contents,
     const std::string& script) {

headless/test/headless_browser_test.h

@@ -74,6 +74,9 @@ class HeadlessBrowserTest : public content::BrowserTestBase {
   // Synchronously waits for a tab to finish loading.
   bool WaitForLoad(HeadlessWebContents* web_contents);
 
+  // Synchronously waits for a tab to finish gaining focus.
+  void WaitForFocus(HeadlessWebContents* web_contents);
+
   // Synchronously evaluates a script and returns the result.
   std::unique_ptr<runtime::EvaluateResult> EvaluateScript(
       HeadlessWebContents* web_contents,