Create the base Custom Context Menu Dialog.

chrome/android/java/src/org/chromium/chrome/browser/contextmenu/ContextMenuHelper.java

Index: chrome/android/java/src/org/chromium/chrome/browser/contextmenu/ContextMenuHelper.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/contextmenu/ContextMenuHelper.java b/chrome/android/java/src/org/chromium/chrome/browser/contextmenu/ContextMenuHelper.java
index 615b7c8fb67885ad79fd377688ec0a8c45c7933d..b27d00e090bd5382f8232c2c855096cdcb678d0d 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/contextmenu/ContextMenuHelper.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/contextmenu/ContextMenuHelper.java
@@ -15,6 +15,7 @@ import org.chromium.base.Callback;
 import org.chromium.base.VisibleForTesting;
 import org.chromium.base.annotations.CalledByNative;
 import org.chromium.base.metrics.RecordHistogram;
+import org.chromium.chrome.browser.ChromeFeatureList;
 import org.chromium.chrome.browser.share.ShareHelper;
 import org.chromium.content.browser.ContentViewCore;
 import org.chromium.content_public.browser.WebContents;
@@ -32,6 +33,7 @@ public class ContextMenuHelper implements OnCreateContextMenuListener {
     private ContextMenuPopulator mPopulator;
     private ContextMenuParams mCurrentContextMenuParams;
     private Activity mActivity;
+    private Callback<Integer> mCallback;
 
     private ContextMenuHelper(long nativeContextMenuHelper) {
         mNativeContextMenuHelper = nativeContextMenuHelper;
@@ -70,12 +72,29 @@ public class ContextMenuHelper implements OnCreateContextMenuListener {
         final WindowAndroid windowAndroid = contentViewCore.getWindowAndroid();
 
         if (view == null || view.getVisibility() != View.VISIBLE || view.getParent() == null
-                || windowAndroid == null || windowAndroid.getActivity().get() == null) {
+                || windowAndroid == null || windowAndroid.getActivity().get() == null
+                || mPopulator == null) {
             return;
         }
 
         mCurrentContextMenuParams = params;
         mActivity = windowAndroid.getActivity().get();
+        mCallback = new Callback<Integer>() {
+            @Override
+            public void onResult(Integer result) {
+                mPopulator.onItemSelected(
+                        ContextMenuHelper.this, mCurrentContextMenuParams, result);
+            }
+        };
+
+        if (ChromeFeatureList.isEnabled(ChromeFeatureList.CUSTOM_CONTEXT_MENU)) {
+            List<Pair<Integer, List<ContextMenuItem>>> items =

[Ted C, 2017/03/24 04:32:53]

I would pull this out and stash it in a local var to share between the two
different UIs.  Then if it is empty, we can early return.

[JJ, 2017/03/25 01:40:25]

So I really really wanted to do this. When separating the callback I thought we
could do this but it turns out doing it like this will cause tests to fail since
the ContextMenu is null. I'm try8ing 

+                    mPopulator.buildContextMenu(null, mActivity, mCurrentContextMenuParams);
+
+            ContextMenuUi menuUi = new TabularContextMenuUi();
+            menuUi.displayMenu(mActivity, mCurrentContextMenuParams, items, mCallback);
+            return;
+        }
 
         view.setOnCreateContextMenuListener(this);
         if (view.showContextMenu()) {
@@ -132,18 +151,10 @@ public class ContextMenuHelper implements OnCreateContextMenuListener {
 
     @Override
     public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) {
-        assert mPopulator != null;
-
         List<Pair<Integer, List<ContextMenuItem>>> items =
                 mPopulator.buildContextMenu(menu, v.getContext(), mCurrentContextMenuParams);
         ContextMenuUi menuUi = new PlatformContextMenuUi(menu);
-        menuUi.displayMenu(mActivity, mCurrentContextMenuParams, items, new Callback<Integer>() {
-            @Override
-            public void onResult(Integer result) {
-                mPopulator.onItemSelected(
-                        ContextMenuHelper.this, mCurrentContextMenuParams, result);
-            }
-        });
+        menuUi.displayMenu(mActivity, mCurrentContextMenuParams, items, mCallback);
     }
 
     /**