Fix <select> popup width

Fix typo in calculation of AnchoredPopupWindow's width.

Bug: 862594
Change-Id: I0f79ca75c1d3c003d24dcba835fb6925b8d1dab5
Reviewed-on: https://chromium-review.googlesource.com/1136723Reviewed-by: Bo <boliu@chromium.org>
Commit-Queue: Amirhossein Simjour <asimjour@chromium.org>
Cr-Commit-Position: refs/heads/master@{#574999}

ui/android/java/src/org/chromium/ui/widget/AnchoredPopupWindow.java

@@ -372,7 +372,7 @@ public class AnchoredPopupWindow implements OnTouchListener, RectProvider.Observ
         int paddingY = mCachedPaddingRect.top + mCachedPaddingRect.bottom;
 
         int maxContentWidth =
-                getMaxContentWidth(mMaxWidthPx, mRootView.getWidth(), mMarginPx, paddingY);
+                getMaxContentWidth(mMaxWidthPx, mRootView.getWidth(), mMarginPx, paddingX);
 
         // Determine whether or not the popup should be above or below the anchor.
         // Aggressively try to put it below the anchor.  Put it above only if it would fit better.