Changes to enable HTML5 autoplay for voice search.

chrome/browser/android/voice_search_tab_helper.cc

Index: chrome/browser/android/voice_search_tab_helper.cc
diff --git a/chrome/browser/android/voice_search_tab_helper.cc b/chrome/browser/android/voice_search_tab_helper.cc
new file mode 100644
index 0000000000000000000000000000000000000000..e640fda8dfc2ddad4176b1e4c559e5de3104b476
--- /dev/null
+++ b/chrome/browser/android/voice_search_tab_helper.cc
@@ -0,0 +1,39 @@
+// Copyright 2013 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 "chrome/browser/android/voice_search_tab_helper.h"
+
+#include "chrome/browser/google/google_util.h"
+#include "content/public/browser/render_view_host.h"
+#include "content/public/browser/web_contents.h"
+#include "jni/VoiceSearchTabHelper_jni.h"
+#include "webkit/common/webpreferences.h"
+
+using content::WebContents;
+
+// Register native methods
+bool RegisterVoiceSearchTabHelper(JNIEnv* env) {
+  return RegisterNativesImpl(env);
+}
+
+static void UpdateAutoplayStatus(JNIEnv* env,
+                                 jobject obj,
+                                 jobject j_web_contents) {
+  WebContents* web_contents = WebContents::FromJavaWebContents(j_web_contents);
+  content::RenderViewHost* host = web_contents->GetRenderViewHost();
+  WebPreferences prefs = host->GetWebkitPreferences();
+
+  // Handle the case where media autoplay has been enabled from the command
+  // line. Or some other override is otherwise in place. This currently fixes
+  // performance tests (see tools/perf/benchmarks/media.py line 33).

[Ted C, 2014/01/03 01:12:24]

Is there any performance impact of building the prefs or the URL comparison
below?  Or is it simply that some performance tests set this to true and expect
it to not change, which is what this class is doing.

Also, I would leave out the file and line number reference as those are very
likely to become stale.  Maybe something like:

// In the case where media autoplay has been enabled by default (e.g. in
// performance media tests), do not update it based on navigation changes.
//
// Note that ...

[apiccion, 2014/01/03 15:43:39]

1. 0.7 ms
2. 0.03 ms
Yes.
Done.

+  //
+  // Note that GetWekitPreferences() is 'stateless'. It returns the default
+  // webkit preferences configuration from command line switches.
+  if (prefs.user_gesture_required_for_media_playback == false)

[Ted C, 2014/01/03 01:12:24]

I think it's more common to use the ! instead of == false

[apiccion, 2014/01/03 15:43:39]

Done.

+    return;
+
+  prefs.user_gesture_required_for_media_playback =
+      !google_util::IsGoogleSearchUrl(web_contents->GetLastCommittedURL());
+  host->UpdateWebkitPreferences(prefs);
+}