Cache the current WebPreferences on RenderViewHostImpl (try #2).

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
index c8f10db3662fae873a0708f60ee2a395dd6b40b3..0782f7578ece106454e03072177956f114b5073f 100644
--- a/chrome/browser/android/voice_search_tab_helper.cc
+++ b/chrome/browser/android/voice_search_tab_helper.cc
@@ -4,9 +4,11 @@
 
 #include "chrome/browser/android/voice_search_tab_helper.h"
 
+#include "base/command_line.h"
 #include "components/google/core/browser/google_util.h"
 #include "content/public/browser/render_view_host.h"
 #include "content/public/browser/web_contents.h"
+#include "content/public/common/content_switches.h"
 #include "content/public/common/web_preferences.h"
 #include "jni/VoiceSearchTabHelper_jni.h"
 
@@ -20,19 +22,25 @@ bool RegisterVoiceSearchTabHelper(JNIEnv* env) {
 static void UpdateAutoplayStatus(JNIEnv* env,
                                  jobject obj,
                                  jobject j_web_contents) {
+  // In the case where media autoplay has been disabled by default (e.g. in
+  // performance media tests) do not update it based on navigation changes.
+  const CommandLine& command_line = *CommandLine::ForCurrentProcess();
+  if (command_line.HasSwitch(
+      switches::kDisableGestureRequirementForMediaPlayback))
+    return;
+
   WebContents* web_contents = WebContents::FromJavaWebContents(j_web_contents);
   content::RenderViewHost* host = web_contents->GetRenderViewHost();
   content::WebPreferences prefs = host->GetWebkitPreferences();
 
-  // 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 GetWekitPreferences() is 'stateless'. It returns the default
-  // webkit preferences configuration from command line switches.
-  if (!prefs.user_gesture_required_for_media_playback)
-    return;
-
-  prefs.user_gesture_required_for_media_playback =
+  bool gesture_required =
       !google_util::IsGoogleSearchUrl(web_contents->GetLastCommittedURL());
-  host->UpdateWebkitPreferences(prefs);
+
+  if (gesture_required != prefs.user_gesture_required_for_media_playback) {
+    // TODO(chrishtr): this is wrong. user_gesture_required_for_media_playback
+    // will be reset the next time a preference changes.
+    prefs.user_gesture_required_for_media_playback =
+        !google_util::IsGoogleSearchUrl(web_contents->GetLastCommittedURL());
+    host->UpdateWebkitPreferences(prefs);
+  }
 }