[Context menu] Return early if a context menu is showing

This CL will be followed up by another one cleaning up the logging
statements once the fix is confirmed.

Bug: 1153706
Change-Id: I2c7feb4b4d94cfd4051df6e64d4564f5a26be16b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2594263Reviewed-by: Theresa  <twellington@chromium.org>
Commit-Queue: Sinan Sahin <sinansahin@google.com>
Cr-Commit-Position: refs/heads/master@{#837392}

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

@@ -114,7 +114,7 @@ public class ContextMenuHelper {
 
         if (view == null || view.getVisibility() != View.VISIBLE || view.getParent() == null
                 || windowAndroid == null || windowAndroid.getActivity().get() == null
-                || mPopulatorFactory == null) {
+                || mPopulatorFactory == null || mCurrentContextMenu != null) {
             return;
         }