Use vector assets for media router icons.

chrome/app/theme/theme_resources.grd

Index: chrome/app/theme/theme_resources.grd
diff --git a/chrome/app/theme/theme_resources.grd b/chrome/app/theme/theme_resources.grd
index f21c2dd86e77608e59c4750df569e44e0909ba19..cc0e1332704bb6fed929dd9fffc474046bf8c8ed 100644
--- a/chrome/app/theme/theme_resources.grd
+++ b/chrome/app/theme/theme_resources.grd
@@ -727,12 +727,6 @@
         <structure type="chrome_scaled_image" name="IDR_AVATAR_THEMED_MAC_BUTTON_NORMAL_TOP_RIGHT" file="mac/avatar_button/sign_in_button_themed_top_right.png" />
       </if>
       <!-- Media Router -->

[apacible, 2016/07/13 22:30:19]

This line can also be removed.

-      <if expr="enable_media_router">
-        <structure type="chrome_scaled_image" name="IDR_MEDIA_ROUTER_ACTIVE_ICON" file="common/media_router_active.png" />
-        <structure type="chrome_scaled_image" name="IDR_MEDIA_ROUTER_ERROR_ICON" file="common/media_router_error.png" />
-        <structure type="chrome_scaled_image" name="IDR_MEDIA_ROUTER_IDLE_ICON" file="common/media_router_idle.png" />
-        <structure type="chrome_scaled_image" name="IDR_MEDIA_ROUTER_WARNING_ICON" file="common/media_router_warning.png" />
-      </if>
       <if expr="enable_app_list">
         <structure type="chrome_scaled_image" name="IDR_PROFILE_PICTURE_LOADING" file="profile_loading.png" />
       </if>