add code to propagate finch config TranslateServerStudy server_params to translate element code

components/translate/core/browser/translate_script.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/translate/core/browser/translate_script.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/profiler/scoped_tracker.h"
 #include "base/single_thread_task_runner.h"
 #include "base/strings/string_piece.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "build/build_config.h"
 #include "components/translate/core/browser/translate_url_fetcher.h"
 #include "components/translate/core/browser/translate_url_util.h"
 #include "components/translate/core/common/translate_switches.h"
 #include "components/translate/core/common/translate_util.h"
+#include "components/variations/variations_associated_data.h"
 #include "google_apis/google_api_keys.h"
 #include "grit/components_resources.h"
 #include "net/base/escape.h"
 #include "net/base/url_util.h"
 #include "ui/base/resource/resource_bundle.h"
 
 namespace translate {
 
 namespace {
 
 const int kExpirationDelayDays = 1;
 
 }  // namespace
 
 const char TranslateScript::kScriptURL[] =
     "https://translate.googleapis.com/translate_a/element.js";
 const char TranslateScript::kRequestHeader[] =
     "Google-Translate-Element-Mode: library";
 const char TranslateScript::kAlwaysUseSslQueryName[] = "aus";
 const char TranslateScript::kAlwaysUseSslQueryValue[] = "true";
 const char TranslateScript::kCallbackQueryName[] = "cb";
 const char TranslateScript::kCallbackQueryValue[] =
     "cr.googleTranslate.onTranslateElementLoad";
 const char TranslateScript::kCssLoaderCallbackQueryName[] = "clc";
 const char TranslateScript::kCssLoaderCallbackQueryValue[] =
     "cr.googleTranslate.onLoadCSS";
 const char TranslateScript::kJavascriptLoaderCallbackQueryName[] = "jlc";
 const char TranslateScript::kJavascriptLoaderCallbackQueryValue[] =
     "cr.googleTranslate.onLoadJavascript";
+const char TranslateScript::kTranslateServerStudy[] = "TranslateServerStudy";
+const char TranslateScript::kServerParams[] = "server_params";
 
 TranslateScript::TranslateScript()
     : expiration_delay_(base::TimeDelta::FromDays(kExpirationDelayDays)),
       weak_method_factory_(this) {
 }
 
 TranslateScript::~TranslateScript() {
 }
 
 void TranslateScript::Request(const RequestCallback& callback) {
@@ skipping 64 matching lines @@
   DCHECK_EQ(kFetcherId, id);
 
   std::unique_ptr<const TranslateURLFetcher> delete_ptr(fetcher_.release());
 
   if (success) {
     DCHECK(data_.empty());
     // Insert variable definitions on API Key and security origin.
     data_ = base::StringPrintf("var translateApiKey = '%s';\n",
                                google_apis::GetAPIKey().c_str());
 
+    // Insert server params to pass experimental params to google translate
+    // server.
+    std::string server_params = "";

[groby-ooo-7-16, 2016/08/02 21:14:10]

No need to initialize - the default ctor automatically creates an empty string. 

[ftang, 2016/08/02 23:46:23]

Done.

+    std::map<std::string, std::string> params;
+    if (variations::GetVariationParams(kTranslateServerStudy,
+                                       &params)) {
+      server_params = params[kServerParams];
+    }
+    base::StringAppendF(
+        &data_, "var serverParams = '%s';\n", server_params.c_str());

[groby-ooo-7-16, 2016/08/02 21:14:10]

I assume this is intentional, and you always want serverParams set, even if the
study didn't have them? (Empty string in that case)

[ftang, 2016/08/02 23:46:23]

YES, I think that will make thing much easier. I can easily check the value in
the js side.

+
     GURL security_origin = translate::GetTranslateSecurityOrigin();
     base::StringAppendF(
         &data_, "var securityOrigin = '%s';", security_origin.spec().c_str());
 
     // Append embedded translate.js and a remote element library.
     base::StringPiece str = ResourceBundle::GetSharedInstance().
         GetRawDataResource(IDR_TRANSLATE_JS);
     str.AppendToString(&data_);
     data_ += data;
 
     // We'll expire the cached script after some time, to make sure long
     // running browsers still get fixes that might get pushed with newer
     // scripts.
     base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
         FROM_HERE,
         base::Bind(&TranslateScript::Clear, weak_method_factory_.GetWeakPtr()),
         expiration_delay_);
   }
 
   for (RequestCallbackList::iterator it = callback_list_.begin();
        it != callback_list_.end();
        ++it) {
     it->Run(success, data);
   }
   callback_list_.clear();
 }
 
 }  // namespace translate