Disable mute/unmute when media does not have an audio track.

chrome/browser/tab_contents/render_view_context_menu.cc

Index: chrome/browser/tab_contents/render_view_context_menu.cc
diff --git a/chrome/browser/tab_contents/render_view_context_menu.cc b/chrome/browser/tab_contents/render_view_context_menu.cc
index 75d02c0a9b2d3b81583d753ed1239059b6f8688c..62cfdbc9663f6240912ff40573808de0b7718c2b 100644
--- a/chrome/browser/tab_contents/render_view_context_menu.cc
+++ b/chrome/browser/tab_contents/render_view_context_menu.cc
@@ -317,12 +317,17 @@ bool RenderViewContextMenu::IsItemCommandEnabled(int id) const {
     // error state.
     case IDS_CONTENT_CONTEXT_PLAY:
     case IDS_CONTENT_CONTEXT_PAUSE:
-    case IDS_CONTENT_CONTEXT_MUTE:
-    case IDS_CONTENT_CONTEXT_UNMUTE:
     case IDS_CONTENT_CONTEXT_LOOP:
       return (params_.media_params.player_state &
               ContextMenuMediaParams::IN_ERROR) == 0;
 
+    // Mute and unmute should also be disabled if the player has no audio.
+    case IDS_CONTENT_CONTEXT_MUTE:
+    case IDS_CONTENT_CONTEXT_UNMUTE:
+      return params_.media_params.has_audio &&
+             (params_.media_params.player_state &
+              ContextMenuMediaParams::IN_ERROR) == 0;
+
     case IDS_CONTENT_CONTEXT_SAVESCREENSHOTAS:
       // TODO(ajwong): Enable save screenshot after we actually implement
       // this.