Merge pull request #149 from UnityTech/iphoneplus_keyboardbug

iphone plus bug fix

Runtime/Plugins/platform/ios/UIWidgetsViewController.mm

     CGFloat bottom = CGRectGetHeight([[info objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue]);
     CGFloat scale = [UIScreen mainScreen].scale;
 
+    // scale == 3 => screen is 1242 * 2208 => we have to perform down-sampling to obtain the real length
+    // 0.8696 = 1920 / 2208, the vertical down-sampling ratio
+    if (scale == 3) {
+        bottom = bottom * 0.8696;
+    }
+
     viewInsets.bottom = bottom * scale;
     padding.bottom = 0;