Add --enable-usermedia-screen-capturing in about:flags

chrome/app/generated_resources.grd

 <?xml version="1.0" encoding="utf-8"?>
 
 <!--
 This file contains definitions of resources that will be translated for each
 locale.  The variables is_win, is_macosx, is_linux, and is_posix are available
 for making strings OS specific.  Other platform defines such as use_titlecase
 are declared in build/common.gypi.
 -->
 
 <grit base_dir="." latest_public_release="0" current_release="1"
@@ skipping 7132 matching lines @@
       </message>
       <message name="IDS_FLAGS_ENABLE_RICH_NOTIFICATIONS_DESCRIPTION" desc="Description for the flag to enable rich notifications.">
         Enable rich templated notifications. Both HTML5 notifications and app notifications will be shown through new Notification Center.
       </message>
       <message name="IDS_FLAGS_ENABLE_SYNC_DICTIONARY_NAME" desc="Name of about:flags option to turn on dictionary sync.">
         Enable dictionary sync
       </message>
       <message name="IDS_FLAGS_ENABLE_SYNC_DICTIONARY_DESCRIPTION" desc="Description of about:flags option to turn on dictionary sync.">
         Enabling syncing the custom spelling dictionary. To view data, visit chrome://settings/editDictionary.
       </message>
+      <message name="IDS_FLAGS_ENABLE_SCREEN_CAPTURE_NAME" desc="Name of the flag to enable screen capture support.">
+        Enable screen capture support in getUserMedia().
+      </message>
+      <message name="IDS_FLAGS_ENABLE_SCREEN_CAPTURE_DESCRIPTION" desc="Description of flag to enable screen capture.">
+        Allow web pages to request access to the screen contents via the getUserMedia() API.
+      </message>
 
       <!-- Crashes -->
       <message name="IDS_CRASHES_TITLE" desc="Title for the chrome://crashes page.">
         Crashes
       </message>
       <message name="IDS_CRASHES_CRASH_COUNT_BANNER_FORMAT" desc="Format for crash count banner on chrome://crashes">
         Crashes (<ph name="CRASH_COUNT">$1<ex>3</ex></ph>)
       </message>
       <message name="IDS_CRASHES_CRASH_HEADER_FORMAT" desc="Format for crash entry headings on chrome://crashes">
         Crash ID <ph name="CRASH_ID">$1<ex>8fa95dbb6f2ec862</ex></ph>
@@ skipping 8709 matching lines @@
 
     <structures fallback_to_english="true">
       <!-- Make sure these stay in sync with the structures in generated_resources.grd. -->
       <structure name="IDD_CHROME_FRAME_FIND_DIALOG" file="cf_resources.rc" type="dialog" >
       </structure>
       <structure name="IDD_CHROME_FRAME_READY_PROMPT" file="cf_resources.rc" type="dialog" >
       </structure>
     </structures>
   </release>
 </grit>