Make URLRequest param is IsWebViewRequest() const.

There's no reason for it be a raw pointer.

BUG=None
Test=None, internal only cleanup.

Review URL: https://codereview.chromium.org/759643007

Cr-Commit-Position: refs/heads/master@{#306695}

extensions/browser/url_request_util.cc

@@ -89,7 +89,7 @@ bool AllowCrossRendererResourceLoad(net::URLRequest* request,
   return false;
 }
 
-bool IsWebViewRequest(net::URLRequest* request) {
+bool IsWebViewRequest(const net::URLRequest* request) {
   const content::ResourceRequestInfo* info =
       content::ResourceRequestInfo::ForRequest(request);
   // |info| can be NULL sometimes: http://crbug.com/370070.

extensions/browser/url_request_util.h

@@ -28,7 +28,7 @@ bool AllowCrossRendererResourceLoad(net::URLRequest* request,
 
 // Returns true if |request| corresponds to a resource request from a
 // <webview>.
-bool IsWebViewRequest(net::URLRequest* request);
+bool IsWebViewRequest(const net::URLRequest* request);
 
 }  // namespace url_request_util
 }  // namespace extensions