Add string resources for media time sliders.

content/child/blink_platform_impl.cc

Index: content/child/blink_platform_impl.cc
diff --git a/content/child/blink_platform_impl.cc b/content/child/blink_platform_impl.cc
index ac9b7a385fb08dffb6749217380dd8e936c22dd2..f7cb48027d43cdff5efd1706933e087e1a627fdd 100644
--- a/content/child/blink_platform_impl.cc
+++ b/content/child/blink_platform_impl.cc
@@ -239,8 +239,10 @@ static int ToMessageID(WebLocalizedString::Name name) {
       return IDS_AX_MEDIA_PLAY_BUTTON_HELP;
     case WebLocalizedString::AXMediaPauseButtonHelp:
       return IDS_AX_MEDIA_PAUSE_BUTTON_HELP;
-    case WebLocalizedString::AXMediaSliderHelp:
-      return IDS_AX_MEDIA_SLIDER_HELP;
+    case WebLocalizedString::AXMediaAudioSliderHelp:
+      return IDS_AX_MEDIA_AUDIO_SLIDER_HELP;
+    case WebLocalizedString::AXMediaVideoSliderHelp:
+      return IDS_AX_MEDIA_VIDEO_SLIDER_HELP;
     case WebLocalizedString::AXMediaSliderThumbHelp:
       return IDS_AX_MEDIA_SLIDER_THUMB_HELP;
     case WebLocalizedString::AXMediaCurrentTimeDisplayHelp: