Fix Android keyboard showing detection

Use the root view's height vs. the visible display frame instead of the screen
height.  This is because the window might not be the full size of the screen.

BUG=251343

Review URL: https://codereview.chromium.org/229903003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@262913 0039d316-1c4b-4281-b951-d872f2087c98

ui/android/java/src/org/chromium/ui/UiUtils.java

@@ -59,10 +59,10 @@ public class UiUtils {
         if (rootView == null) return false;
         Rect appRect = new Rect();
         rootView.getWindowVisibleDisplayFrame(appRect);
-        final float screenHeight = context.getResources().getDisplayMetrics().heightPixels;
-        final float bottomMargin = Math.abs(appRect.bottom - screenHeight);
+
         final float density = context.getResources().getDisplayMetrics().density;
-        return bottomMargin > KEYBOARD_DETECT_BOTTOM_THRESHOLD_DP * density;
+        final float bottomMarginDp = Math.abs(rootView.getHeight() - appRect.height()) / density;
+        return bottomMarginDp > KEYBOARD_DETECT_BOTTOM_THRESHOLD_DP;
     }
 
     /**