Fix issues related to request and context object lifespan (issue #1037, issue #1044).

- Simplify and document the relationship between the various context object types. See browser_context.h for a description of the new relationships.
- cefclient: Add `request-context-per-browser` command-line flag for testing multiple CefRequestContext instances.
- cefclient: Add a CefURLRequest example.

git-svn-id: https://chromiumembedded.googlecode.com/svn/trunk@2032 5089003a-bbd8-11dd-ad1f-f1f9622dbc98

libcef/browser/scheme_impl.cc

@@ -196,9 +196,8 @@ class CefUrlRequestManager {
 
  private:
   net::URLRequestJobFactoryImpl* GetJobFactoryImpl() {
-    return static_cast<CefURLRequestContextGetter*>(
-        CefContentBrowserClient::Get()->request_context().get())->
-            job_factory_impl();
+    return CefContentBrowserClient::Get()->request_context()->
+        job_factory_impl();
   }
 
   // Add or remove the protocol handler if necessary. |scheme| will already be