Improve error messaging of webRequest API in case of conflicts

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 28211a101ec80db4f38838253dba3e3cc4218ed4..21773f83a7553f9320eb761fd2ea74aae00b0d97 100644
--- a/chrome/app/generated_resources.grd
+++ b/chrome/app/generated_resources.grd
@@ -5503,6 +5503,18 @@ Keep your key file in a safe place. You will need it to create new versions of y
       <message name="IDS_EXTENSION_WARNINGS_NETWORK_CONFLICT" desc="Warning message which indicates that two or more extensions tried to modify a network request in a conflicting way and the modification of this extension was ignored">
         This extension failed to modify a network request because the modification conflicted with another extension.
       </message>
+      <message name="IDS_EXTENSION_WARNINGS_REDIRECT_CONFLICT" desc="Warning message indicating that two extensions tried to redirect to different destinations">
+        This extension failed to redirect a network request to <ph name="ATTEMPTED_REDIRECT_DESTINATION">$1<ex>http://www.google.com</ex></ph> because another extension (<ph name="EXTENSION_NAME">$2<ex>My Cool Extension</ex></ph>) redirected it to <ph name="ACTUAL_REDIRECT_DESTINATION">$3<ex>https://www.google.com</ex></ph>.
+      </message>
+      <message name="IDS_EXTENSION_WARNINGS_REQUEST_HEADER_CONFLICT" desc="Warning message which indicates that two or more extensions tried to modify a network request in a conflicting way and the modification of this extension was ignored">
+        This extension failed to modify the request header "<ph name="HEADER_NAME">$1<ex>User-Agent</ex></ph>" of a network request because the modification conflicted with another extension (<ph name="EXTENSION_NAME">$2<ex>My Cool Extension</ex></ph>).
+      </message>
+      <message name="IDS_EXTENSION_WARNINGS_RESPONSE_HEADER_CONFLICT" desc="Warning message which indicates that two or more extensions tried to modify a network request in a conflicting way and the modification of this extension was ignored">
+        This extension failed to modify the response header "<ph name="HEADER_NAME">$1<ex>User-Agents</ex></ph>" of a network request because the modification conflicted with another extension (<ph name="EXTENSION_NAME">$2<ex>My Cool Extension</ex></ph>).
+      </message>
+      <message name="IDS_EXTENSION_WARNINGS_CREDENTIALS_CONFLICT" desc="Warning message which indicates that two or more extensions tried to modify a network request in a conflicting way and the modification of this extension was ignored">
+        This extension failed to provide credentials to a network request because another extension (<ph name="EXTENSION_NAME">$1<ex>My Cool Extension</ex></ph>) provided different credentials.
+      </message>
 
       <!-- External extension install alerts -->
       <!-- TODO(mpcomplete): We may need to change Chrome to