Media Remoting: Add interstitial elements to media element shadow dom.

third_party/WebKit/Source/modules/accessibility/AXMediaControls.cpp

Index: third_party/WebKit/Source/modules/accessibility/AXMediaControls.cpp
diff --git a/third_party/WebKit/Source/modules/accessibility/AXMediaControls.cpp b/third_party/WebKit/Source/modules/accessibility/AXMediaControls.cpp
index 16b35e7eab9653b3e002e9d1ff4f49d2c828b13f..d522fa85c05ed30e7ea6bd06a136ee9d7b784000 100644
--- a/third_party/WebKit/Source/modules/accessibility/AXMediaControls.cpp
+++ b/third_party/WebKit/Source/modules/accessibility/AXMediaControls.cpp
@@ -84,6 +84,7 @@ AXObject* AccessibilityMediaControl::create(LayoutObject* layoutObject,
     case MediaOverflowButton:
     case MediaOverflowList:
     case MediaDownloadButton:
+    case MediaRemotingCastIcon:
       return new AccessibilityMediaControl(layoutObject, axObjectCache);
   }
 
@@ -150,6 +151,8 @@ String AccessibilityMediaControl::textAlternative(
     case MediaSlider:
       NOTREACHED();
       return queryString(WebLocalizedString::AXMediaDefault);
+    case MediaRemotingCastIcon:
+      return queryString(WebLocalizedString::AXMediaRemotingCastIcon);
   }
 
   NOTREACHED();
@@ -206,6 +209,8 @@ String AccessibilityMediaControl::description(
     case MediaSlider:
       NOTREACHED();
       return queryString(WebLocalizedString::AXMediaDefault);
+    case MediaRemotingCastIcon:
+      return queryString(WebLocalizedString::AXMediaRemotingCastIconHelp);
   }
 
   NOTREACHED();
@@ -239,6 +244,7 @@ AccessibilityRole AccessibilityMediaControl::roleValue() const {
     case MediaDownloadButton:
     case MediaCastOnButton:
     case MediaCastOffButton:
+    case MediaRemotingCastIcon:
       return ButtonRole;
 
     case MediaTimelineContainer: