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

tests/cefclient/browser/test_runner.h

@@ -27,6 +27,9 @@ std::string DumpRequestContents(CefRefPtr<CefRequest> request);
 std::string GetDataURI(const std::string& data,
                        const std::string& mime_type);
 
+// Returns the string representation of the specified error code.
+std::string GetErrorString(cef_errorcode_t code);
+
 // Get test resources.
 CefRefPtr<CefResourceHandler> GetResourceHandler(
     CefRefPtr<CefBrowser> browser,