add experimental param to control the triggering threshold to default Always Translate checked

components/translate/core/browser/translate_ui_delegate.cc

Index: components/translate/core/browser/translate_ui_delegate.cc
diff --git a/components/translate/core/browser/translate_ui_delegate.cc b/components/translate/core/browser/translate_ui_delegate.cc
index 50879397171f0a66a0c9c50180aea59e27d7a43e..694c5888c217e5f97e616d575cbafe4b51da6e6b 100644
--- a/components/translate/core/browser/translate_ui_delegate.cc
+++ b/components/translate/core/browser/translate_ui_delegate.cc
@@ -6,6 +6,7 @@
 
 #include "base/i18n/string_compare.h"
 #include "base/metrics/histogram_macros.h"
+#include "base/strings/string_number_conversions.h"
 #include "components/translate/core/browser/language_state.h"
 #include "components/translate/core/browser/translate_client.h"
 #include "components/translate/core/browser/translate_download_manager.h"
@@ -13,6 +14,7 @@
 #include "components/translate/core/browser/translate_manager.h"
 #include "components/translate/core/browser/translate_prefs.h"
 #include "components/translate/core/common/translate_constants.h"
+#include "components/variations/variations_associated_data.h"
 #include "third_party/icu/source/i18n/unicode/coll.h"
 #include "ui/base/l10n/l10n_util.h"
 
@@ -302,14 +304,35 @@ bool TranslateUIDelegate::ShouldAlwaysTranslate() {
 }
 
 bool TranslateUIDelegate::ShouldAlwaysTranslateBeCheckedByDefault() {
-  // After 2 clicks on Translate for the same language.
-  // We check for == 2 instead of >= 2 because if the user translates with the
+  if (ShouldAlwaysTranslate())
+    return true;
+
+  std::map<std::string, std::string> params;
+  int always_translate_offer_threshold = -1;
+  if (variations::GetVariationParams(translate::kTranslateUI2016Q2TrialName,
+                                     &params)) {
+    auto it = params.find(translate::kAlwaysTranslateOfferThreshold);

[groby-ooo-7-16, 2016/06/28 17:35:20]

Why not the shorter variant? (I'm fine with using find, I'm just curious)

[ftang, 2016/06/28 21:51:12]

Done.

+    if (it != params.end()) {
+      if (!base::StringToInt(it->second, &always_translate_offer_threshold)) {
+        // if we cannot parse the number, return false.
+        return false;
+      }
+    }
+  }
+
+  if (always_translate_offer_threshold < 0) {

[groby-ooo-7-16, 2016/06/28 17:35:20]

<= 0?

[ftang, 2016/06/28 21:51:12]

Done.

+    // if the number is negative, we never set the checked by default.
+    return false;
+  }
+
+  // After N clicks on Translate for the same language.
+  // We check for == N instead of >= N because if the user translates with the
   // "Always do this?" on, then the next time the bubble won't show up.
   // The only chance the bubble will show up is after the user manually unchecks
   // "Always do this?". In that case, since it is after user explictly unchecks,
-  // we should show as it as unchecked so we only check == 2 instead of >= 2.
-  return ShouldAlwaysTranslate() ||
-         prefs_->GetTranslationAcceptedCount(GetOriginalLanguageCode()) == 2;
+  // we should show as it as unchecked so we only check == N instead of >= N.
+  return prefs_->GetTranslationAcceptedCount(GetOriginalLanguageCode()) ==

[groby-ooo-7-16, 2016/06/28 17:35:20]

You really want greater-equals here. Otherwise, you miss all the cases where
users already have a sufficient accept count before they receive this upgrade.

[ftang, 2016/06/28 21:51:12]

The problem of that is, then if the user explicitly uncheck the checked
checkbox, it will show up again as checked the next time, which is not the right
thing to do. 

+         always_translate_offer_threshold;
 }
 
 void TranslateUIDelegate::SetAlwaysTranslate(bool value) {