Factor out core logic from OnCanAccessFile() and add tests for it

chrome/browser/net/chrome_network_delegate.h

Index: chrome/browser/net/chrome_network_delegate.h
diff --git a/chrome/browser/net/chrome_network_delegate.h b/chrome/browser/net/chrome_network_delegate.h
index 759a0e5216843c879e9e3bb1099c8b2edf67471f..e3636c0798803679abf656f275b31f6c98f1b619 100644
--- a/chrome/browser/net/chrome_network_delegate.h
+++ b/chrome/browser/net/chrome_network_delegate.h
@@ -77,9 +77,9 @@ class ChromeNetworkDelegate : public net::NetworkDelegateImpl {
   // Also pass through to ChromeExtensionsNetworkDelegate::set_profile().
   void set_profile(void* profile);
 
-  // |profile_path| is used to locate the "Downloads" folder on Chrome OS. If it
-  // is set, the location of the Downloads folder for the profile is added to
-  // the whitelist for accesses via file: scheme.
+  // |profile_path| is used to locate profile specific paths such as the
+  // "Downloads" folder on Chrome OS. If it is set, folders like Downloads
+  // for the profile are added to the whitelist for accesses via file: scheme.
   void set_profile_path(const base::FilePath& profile_path) {
     profile_path_ = profile_path;
   }
@@ -129,6 +129,11 @@ class ChromeNetworkDelegate : public net::NetworkDelegateImpl {
       StringPrefMember* allowed_domains_for_apps,
       PrefService* pref_service);
 
+  // Returns true if access to |path| is allowed. |profile_path| is used to
+  // locate certain paths on Chrome OS. See set_profile_path() for details.
+  static bool IsAccessAllowed(const base::FilePath& path,
+                              const base::FilePath& profile_path);
+
  private:
   // NetworkDelegate implementation.
   int OnBeforeURLRequest(net::URLRequest* request,