Implement offline mode behind a flag

chrome/app/generated_resources.grd

Index: chrome/app/generated_resources.grd
diff --git a/chrome/app/generated_resources.grd b/chrome/app/generated_resources.grd
index 9ceae84bfb018d2ef20f67041e48081b7f6093ea..ac8120c8fece34b27ee839eec06f3b2894cdc725 100644
--- a/chrome/app/generated_resources.grd
+++ b/chrome/app/generated_resources.grd
@@ -15191,6 +15191,12 @@ Some features may be unavailable.  Please check that the profile exists and you
     <message name="IDS_FLAGS_ENABLE_GOOGLE_NOW_INTEGRATION_DESCRIPTION" desc="Description of about:flags option to turn on Google Now integration">
       Enable Google Now notifications support.
     </message>
+    <message name="IDS_FLAGS_ENABLE_OFFLINE_MODE_NAME" desc="Name of the flag to make reads in offline mode come from the cache even if it's stale">
+      Enable Offline Cache Mode
+    </message>
+    <message name="IDS_FLAGS_ENABLE_OFFLINE_MODE_DESCRIPTION" desc="Description of the flag to make reads in offline mode come from the cache even if it's stale">
+      Reads from web resources when the source is unavailable will be satisfied from available stale cache entries.  
+    </message>
 
     <!-- Toast experiment. -->
     <message name="IDS_TRY_TOAST_SET_DEFAULT" desc="Text of the checkbox to make chrome the default browser">