Create the base Custom Context Menu Dialog.

chrome/browser/android/chrome_feature_list.cc

Index: chrome/browser/android/chrome_feature_list.cc
diff --git a/chrome/browser/android/chrome_feature_list.cc b/chrome/browser/android/chrome_feature_list.cc
index e313b4f7c19ed235131ac5cc2067477102dc4182..53e3cc1ae4bc82fddb2e399651520a493f6f660f 100644
--- a/chrome/browser/android/chrome_feature_list.cc
+++ b/chrome/browser/android/chrome_feature_list.cc
@@ -51,6 +51,7 @@ const base::Feature* kFeaturesExposedToJava[] = {
     &kChromeHomeFeature,
     &kContextualSearchSingleActions,
     &kContextualSearchUrlActions,
+    &kCustomContextMenu,
     &kCustomFeedbackUi,
     &kImportantSitesInCBD,
     &kImprovedA2HS,
@@ -87,8 +88,8 @@ const base::Feature* FindFeatureExposedToJava(const std::string& feature_name) {
     if (kFeaturesExposedToJava[i]->name == feature_name)
       return kFeaturesExposedToJava[i];
   }
-  NOTREACHED() << "Queried feature cannot be found in ChromeFeatureList: "
-               << feature_name;
+  NOTREACHED() << "Features queried via ChromeFeatureList must be present in "

[JJ, 2017/03/17 21:12:43]

Absolutely unintentional, fixed in next patch.

+                  "|kFeaturesExposedToJava|.";
   return nullptr;
 }
 
@@ -122,6 +123,9 @@ const base::Feature kContextualSearchSingleActions{
 const base::Feature kContextualSearchUrlActions{
     "ContextualSearchUrlActions", base::FEATURE_DISABLED_BY_DEFAULT};
 
+const base::Feature kCustomContextMenu{"CustomContextMenu",
+                                       base::FEATURE_DISABLED_BY_DEFAULT};
+
 const base::Feature kCustomFeedbackUi{"CustomFeedbackUi",
                                       base::FEATURE_DISABLED_BY_DEFAULT};