Request debug headers and log URL correctly

Merged from https://widevine-internal-review.googlesource.com/165861

We want debug headers to help diagnose b/186031735. I also
saw that we were only logging the domain name for some
errors instead of the full URL.

Bug: 186031735
Test: GtsMediaTestCases
Change-Id: I4d469a73e54f86d4d3b5d50bd0030fdb2a36df50

libwvdrmengine/cdm/core/test/http_socket.h

@@ -32,6 +32,9 @@ class HttpSocket {
   const std::string& domain_name() const { return domain_name_; }
   int port() const { return atoi(port_.c_str()); }
   const std::string& resource_path() const { return resource_path_; }
+  std::string url() const {
+    return scheme_ + "://" + domain_name_ + ":" + port_ + resource_path_;
+  }
 
   int ReadAndLogErrors(char* data, int len, int timeout_in_ms);
   int WriteAndLogErrors(const char* data, int len, int timeout_in_ms);