Do not attempt to show the paste popup if the view is detached.

BUG=581949

Review URL: https://codereview.chromium.org/1648783003

Cr-Commit-Position: refs/heads/master@{#372188}

content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java

@@ -2539,6 +2539,10 @@ public class ContentViewCore implements AccessibilityStateChangeListener, Screen
     }
 
     private boolean showPastePopup(int x, int y) {
+        if (mContainerView.getParent() == null || mContainerView.getVisibility() != View.VISIBLE) {
+            return false;
+        }
+
         if (!mHasInsertion || !canPaste()) return false;
         final float contentOffsetYPix = mRenderCoordinates.getContentOffsetYPix();
         getPastePopup().show(x, (int) (y + contentOffsetYPix));