Bug 1155819 - Set anchor as back button for tablets. r=ally

--HG--
extra : rebase_source : 0e877a56a15b14b4cc35c4a6744e17666b745b02

mobile/android/base/toolbar/BrowserToolbarTabletBase.java

@@ -127,6 +127,11 @@ abstract class BrowserToolbarTabletBase extends BrowserToolbar {
         }
     }
 
+    @Override
+    public View getDoorHangerAnchor() {
+        return backButton;
+    }
+
     protected boolean canDoBack(final Tab tab) {
         return (tab.canDoBack() && !isEditing());
     }

mobile/android/base/widget/AnchoredPopup.java

@@ -100,11 +100,15 @@ public abstract class AnchoredPopup extends PopupWindow {
             return;
         }
 
-        // If the anchor is null or out of the window bounds, just show the popup at the top of the
-        // root view.
-        final boolean validAnchor = (mAnchor != null) && (anchorLocation[1] > 0);
-        final View anchor = validAnchor ? mAnchor : decorView;
+        if (HardwareUtils.isTablet()) {
+            showAsDropDown(mAnchor, 0, 0);
+        } else {
+            // If the anchor is null or out of the window bounds, just show the popup at the top of the
+            // root view.
+            final boolean validAnchor = (mAnchor != null) && (anchorLocation[1] > 0);
+            final View anchor = validAnchor ? mAnchor : decorView;
 
-        showAtLocation(anchor, Gravity.TOP | Gravity.CENTER_HORIZONTAL, 0, offsetY);
+            showAtLocation(anchor, Gravity.TOP | Gravity.CENTER_HORIZONTAL, 0, offsetY);
+        }
     }
 }