Allow content to get the system request context, a request context not tied to any profile.

content/browser/content_browser_client.h

Index: content/browser/content_browser_client.h
diff --git a/content/browser/content_browser_client.h b/content/browser/content_browser_client.h
index 62550cc50ae33a356cdb75b252c2c1a63215d9b6..7fdff598a10d8ada0af30b14123db4d3c094e12a 100644
--- a/content/browser/content_browser_client.h
+++ b/content/browser/content_browser_client.h
@@ -287,6 +287,10 @@ class ContentBrowserClient {
   virtual net::URLRequestContextGetter*
       GetDefaultRequestContextDeprecatedCrBug64339() = 0;
 
+  // Returns the system request context, a context tied to no browser context.
+  // This is called on the UI thread.
+  virtual net::URLRequestContextGetter* GetSystemRequestContext() = 0;
+
 #if defined(OS_POSIX) && !defined(OS_MACOSX)
   // Can return an optional fd for crash handling, otherwise returns -1.
   virtual int GetCrashSignalFD(const std::string& process_type) = 0;