Set User-Agent and Accept-Language request headers for PWS requests

net/http/http_util.cc

Index: net/http/http_util.cc
diff --git a/net/http/http_util.cc b/net/http/http_util.cc
index 06fc15edd3668e367d0551cf4314de04beb73c65..18ce10d34a5462419a3375f5f190abb3be8e475a 100644
--- a/net/http/http_util.cc
+++ b/net/http/http_util.cc
@@ -755,6 +755,10 @@ std::string HttpUtil::ConvertHeadersBackToHTTPResponse(const std::string& str) {
 // without any whitespace. As long as it comes from the preference and
 // a user does not manually edit the preference file, it's the case. Still,
 // we may have to make it more robust.
+// 3. The logic here is duplicated by generateAcceptLanguageHeader in
+// chrome/android/java/src/org/chromium/chrome/browser/
+//     physicalweb/PwsClientImpl.java
+// The two implementations should be kept in sync.

[asanka, 2016/05/27 16:57:59]

Let's remove this comment. I don't think its feasible to keep C++ and Java login
in sync via comments like these.

Is the PWS a purely Java implementation?

[mattreynolds, 2016/05/27 17:24:11]

The Physical Web client in Chrome for Android is by necessity implemented in
Java.  We don't want to load the native layer to resolve URLs or show
notifications when Chrome is in the background.

[asanka, 2016/06/01 20:10:26]

Understood. Thanks for removing the comment.

Would it be possible to determine the UA and Accept-Language headers while the
native portion is loaded and persist it somewhere for the Java code to access?
That way you won't need to worry about the languages preferences mismatches due
to duplicated code going out of sync. I imagine it would reduce the maintenance
burden and reduce the risk of subtle mysterious breakages down the line that
will probably remain unfixed.

[mattreynolds, 2016/06/01 22:02:48]

Yes, we could store it in SharedPreferences and update at a time when we know
native is loaded (eg, at Chrome startup).  However this would cause the header
to be out of sync whenever the user changes the system locale without restarting
Chrome.

 std::string HttpUtil::GenerateAcceptLanguageHeader(
     const std::string& raw_language_list) {
   // We use integers for qvalue and qvalue decrement that are 10 times