[Media] Add a Finch experiment to enable the permission bubble request.

chrome/browser/media/media_capture_devices_dispatcher.cc

Index: chrome/browser/media/media_capture_devices_dispatcher.cc
diff --git a/chrome/browser/media/media_capture_devices_dispatcher.cc b/chrome/browser/media/media_capture_devices_dispatcher.cc
index 45fb447f612d58e820ed6eb8986ab84297c5e94e..87fcb2a6c934ba93745107a19ee0417236f7cf5b 100644
--- a/chrome/browser/media/media_capture_devices_dispatcher.cc
+++ b/chrome/browser/media/media_capture_devices_dispatcher.cc
@@ -8,6 +8,7 @@
 #include "apps/app_window_registry.h"
 #include "base/command_line.h"
 #include "base/logging.h"
+#include "base/metrics/field_trial.h"
 #include "base/prefs/pref_service.h"
 #include "base/prefs/scoped_user_pref_update.h"
 #include "base/sha1.h"
@@ -64,6 +65,16 @@ using content::MediaStreamDevices;
 
 namespace {
 
+// A finch experiment to enable the permission bubble for media requests only.
+bool MediaStreamPermissionBubbleExperimentEnabled() {
+  const std::string group =
+      base::FieldTrialList::FindFullName("MediaStreamPermissionBubble");
+  if (group == "enabled")
+    return true;
+
+  return false;
+}
+
 // Finds a device in |devices| that has |device_id|, or NULL if not found.
 const content::MediaStreamDevice* FindDeviceWithId(
     const content::MediaStreamDevices& devices,
@@ -623,7 +634,8 @@ void MediaCaptureDevicesDispatcher::ProcessQueuedAccessRequest(
 
   DCHECK(!it->second.empty());
 
-  if (PermissionBubbleManager::Enabled()) {
+  if (PermissionBubbleManager::Enabled() ||
+      MediaStreamPermissionBubbleExperimentEnabled()) {
     scoped_ptr<MediaStreamDevicesController> controller(
         new MediaStreamDevicesController(web_contents,
             it->second.front().request,