- 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/internal/cef_types.h

@@ -2299,6 +2299,48 @@ typedef enum {
   PLUGIN_POLICY_DISABLE,
 } cef_plugin_policy_t;
 
+///
+// Policy for how the Referrer HTTP header value will be sent during navigation.
+// If the `--no-referrers` command-line flag is specified then the policy value
+// will be ignored and the Referrer value will never be sent.
+///
+typedef enum  {
+  ///
+  // Always send the complete Referrer value.
+  ///
+  REFERRER_POLICY_ALWAYS,
+
+  ///
+  // Use the default policy. This is REFERRER_POLICY_ORIGIN_WHEN_CROSS_ORIGIN
+  // when the `--reduced-referrer-granularity` command-line flag is specified
+  // and REFERRER_POLICY_NO_REFERRER_WHEN_DOWNGRADE otherwise.
+  //
+  ///
+  REFERRER_POLICY_DEFAULT,
+
+  ///
+  // When navigating from HTTPS to HTTP do not send the Referrer value.
+  // Otherwise, send the complete Referrer value.
+  ///
+  REFERRER_POLICY_NO_REFERRER_WHEN_DOWNGRADE,
+
+  ///
+  // Never send the Referrer value.
+  ///
+  REFERRER_POLICY_NEVER,
+
+  ///
+  // Only send the origin component of the Referrer value.
+  ///
+  REFERRER_POLICY_ORIGIN,
+
+  ///
+  // When navigating cross-origin only send the origin component of the Referrer
+  // value. Otherwise, send the complete Referrer value.
+  ///
+  REFERRER_POLICY_ORIGIN_WHEN_CROSS_ORIGIN,
+} cef_referrer_policy_t;
+
 #ifdef __cplusplus
 }
 #endif