Fix payload iteration issue of FormBody; Log form body; ignore body for response of HEAD.

webcc/response_parser.h

@@ -17,12 +17,24 @@ public:
 
   void Init(Response* response);
 
+  void set_ignroe_body(bool ignroe_body) {
+    ignroe_body_ = ignroe_body;
+  }
+
 private:
   // Parse HTTP start line; E.g., "HTTP/1.1 200 OK".
   bool ParseStartLine(const std::string& line) override;
 
+  // Override to allow to ignore the body of the response for HEAD request.
+  bool ParseContent(const char* data, std::size_t length) override;
+
+private:
   // The result response message.
   Response* response_;
+
+  // The response for HEAD request could also have `Content-Length` header,
+  // set this flag to ignore it.
+  bool ignroe_body_ = false;
 };
 
 }  // namespace webcc