Defer media playback in background tabs.

chrome/browser/media/defer_background_media_browsertest.cc

Index: chrome/browser/media/defer_background_media_browsertest.cc
diff --git a/chrome/browser/media/defer_background_media_browsertest.cc b/chrome/browser/media/defer_background_media_browsertest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..9d1970b77adf378aa35c235140f1eca353f7f423
--- /dev/null
+++ b/chrome/browser/media/defer_background_media_browsertest.cc
@@ -0,0 +1,58 @@
+// 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/strings/stringprintf.h"

[Lei Zhang, 2015/08/14 02:21:18]

not used

[DaleCurtis, 2015/08/18 18:19:12]

Done.

+#include "base/strings/utf_string_conversions.h"
+#include "build/build_config.h"
+#include "chrome/browser/ui/browser.h"
+#include "chrome/browser/ui/tabs/tab_strip_model.h"
+#include "chrome/test/base/in_process_browser_test.h"
+#include "chrome/test/base/ui_test_utils.h"
+#include "content/public/test/browser_test_utils.h"
+#include "media/base/test_data_util.h"
+
+// Android does not support deferred media loading.

[Lei Zhang, 2015/08/14 02:21:18]

Add bug # if there is one

[mmenke, 2015/08/14 14:57:35]

Does this mean if we prerender on android, we'll play any audio?

[DaleCurtis, 2015/08/14 17:37:35]

The DeferMediaLoad() call is unused on Android (see the dropped callback in the
WebMediaPlayerAndroid constructor) so if you were to enable prerendering on
Android you'd need to fix that -- though for user who haven't disabled it, the
autoplay requirement of a user gesture prevents playback anyways.

[mmenke, 2015/08/18 17:36:04]

I believe prerendering is enabled on Android, or at least some stuff directly
uses the prerendering mechanism - see, for example,
chrome/browser/android/omnibox/omnibox_prerender.h.

[DaleCurtis, 2015/08/18 18:19:12]

Hmm, that's broken for Media Source on Android then and only working because we
require a user gesture for media playback. For src= playback it looks like the
Android MediaPlayer path does seem to try and check for prerendering via an
alternate mechanism:

https://code.google.com/p/chromium/codesearch#chromium/src/content/browser/me...

However that check does not work, any user which flag flips the user gesture
requirement to off is getting autoplay on prerendered pages. I just confirmed
this by creating a prerender test page and navigating to
http://commondatastorage.googleapis.com/dalecurtis-shared/prerender.html

Filed http://crbug.com/522157 -- which I'll try to fix after landing this
change.

+#if !defined(OS_ANDROID)
+typedef InProcessBrowserTest MediaBrowserTest;
+
+IN_PROC_BROWSER_TEST_F(MediaBrowserTest, BackgroundMediaIsDeferred) {
+  // Navigate to a video file, which would autoplay in the foreground, but won't
+  // in the background due to deferred media loading for hidden tabs.
+  ui_test_utils::NavigateToURLWithDisposition(
+      browser(), content::GetFileUrlWithQuery(
+                     media::GetTestDataFilePath("bear-640x360.webm"), ""),
+      NEW_BACKGROUND_TAB, ui_test_utils::BROWSER_TEST_WAIT_FOR_NAVIGATION);
+
+  ASSERT_EQ(2, browser()->tab_strip_model()->count());
+  content::WebContents* background_contents =

[Lei Zhang, 2015/08/14 02:21:18]

Also get the current tab via GetActiveWebContents() before opening a new one and
check that != background_contents as a sanity check?

[DaleCurtis, 2015/08/18 18:19:12]

Done.

+      browser()->tab_strip_model()->GetWebContentsAt(1);
+  EXPECT_TRUE(
+      content::WaitForRenderFrameReady(background_contents->GetMainFrame()));
+
+  // If autoplay for background tabs isn't deferred the play event listener will
+  // be attached too late to catch the event, and subsequently the test will hit
+  // the ended event before the play event.
+  EXPECT_TRUE(
+      content::ExecuteScript(background_contents,
+                             "var video = document.querySelector('video');"
+                             "video.addEventListener('ended', function(event) {"
+                             "  document.title = 'ended';"
+                             "}, false);"
+                             "video.addEventListener('play', function(event) {"
+                             "  document.title = 'playing';"
+                             "}, false);"));
+
+  // Make the background tab w/ our video the active tab.
+  browser()->tab_strip_model()->SelectNextTab();
+  EXPECT_EQ(background_contents,
+            browser()->tab_strip_model()->GetActiveWebContents());
+
+  // If everything worked, we should see "playing" and not "ended".
+  const base::string16 playing_str = base::UTF8ToUTF16("playing");
+  const base::string16 ended_str = base::UTF8ToUTF16("ended");
+  content::TitleWatcher watcher(background_contents, playing_str);
+  watcher.AlsoWaitForTitle(ended_str);
+  EXPECT_EQ(playing_str, watcher.WaitAndGetTitle());
+}
+#endif

[Lei Zhang, 2015/08/14 02:21:18]

// !defined(OS_ANDROID)

[DaleCurtis, 2015/08/18 18:19:12]

Done.