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

components/translate/core/browser/translate_script.cc

Index: components/translate/core/browser/translate_script.cc
diff --git a/components/translate/core/browser/translate_script.cc b/components/translate/core/browser/translate_script.cc
index 511ac6c9057f43a17e42fa0c7e400b8662e0c58a..f75de95820be9e0708e7bdb26279b7c6796f37de 100644
--- a/components/translate/core/browser/translate_script.cc
+++ b/components/translate/core/browser/translate_script.cc
@@ -19,6 +19,7 @@
 #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"
@@ -48,6 +49,8 @@ const char TranslateScript::kCssLoaderCallbackQueryValue[] =
 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)),
@@ -132,6 +135,17 @@ void TranslateScript::OnScriptFetchComplete(
     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());