- Add CefPostData::HasExcludedElements which returns true if the underlying

POST data includes elements that are not represented (issue #1761).
- Add CefRequest::SetReferrer and CefRequest::GetReferrer[URL|Policy]. The
  Referer value will no longer be stored in the header map.
- Move request-related conversion logic to CefRequestImpl and standardize the
  implementation.

include/capi/cef_request_capi.h

@@ -87,6 +87,27 @@ typedef struct _cef_request_t {
   void (CEF_CALLBACK *set_method)(struct _cef_request_t* self,
       const cef_string_t* method);
 
+  ///
+  // Set the referrer URL and policy. If non-NULL the referrer URL must be fully
+  // qualified with an HTTP or HTTPS scheme component. Any username, password or
+  // ref component will be removed.
+  ///
+  void (CEF_CALLBACK *set_referrer)(struct _cef_request_t* self,
+      const cef_string_t* referrer_url, cef_referrer_policy_t policy);
+
+  ///
+  // Get the referrer URL.
+  ///
+  // The resulting string must be freed by calling cef_string_userfree_free().
+  cef_string_userfree_t (CEF_CALLBACK *get_referrer_url)(
+      struct _cef_request_t* self);
+
+  ///
+  // Get the referrer policy.
+  ///
+  cef_referrer_policy_t (CEF_CALLBACK *get_referrer_policy)(
+      struct _cef_request_t* self);
+
   ///
   // Get the post data.
   ///
@@ -100,13 +121,14 @@ typedef struct _cef_request_t {
       struct _cef_post_data_t* postData);
 
   ///
-  // Get the header values.
+  // Get the header values. Will not include the Referer value if any.
   ///
   void (CEF_CALLBACK *get_header_map)(struct _cef_request_t* self,
       cef_string_multimap_t headerMap);
 
   ///
-  // Set the header values.
+  // Set the header values. If a Referer value exists in the header map it will
+  // be removed and ignored.
   ///
   void (CEF_CALLBACK *set_header_map)(struct _cef_request_t* self,
       cef_string_multimap_t headerMap);
@@ -190,6 +212,14 @@ typedef struct _cef_post_data_t {
   ///
   int (CEF_CALLBACK *is_read_only)(struct _cef_post_data_t* self);
 
+  ///
+  // Returns true (1) if the underlying POST data includes elements that are not
+  // represented by this cef_post_data_t object (for example, multi-part file
+  // upload data). Modifying cef_post_data_t objects with excluded elements may
+  // result in the request failing.
+  ///
+  int (CEF_CALLBACK *has_excluded_elements)(struct _cef_post_data_t* self);
+
   ///
   // Returns the number of existing post data elements.
   ///