Fix widget span

Need to take the horizontal margin of the view into consideration.

Fix: 233302799
Test: manual
Change-Id: I5f584977db85d5436b22c3701f586a5b079099ae
diff --git a/src/com/android/launcher3/widget/BaseWidgetSheet.java b/src/com/android/launcher3/widget/BaseWidgetSheet.java
index 1bcba14..8962c4f 100644
--- a/src/com/android/launcher3/widget/BaseWidgetSheet.java
+++ b/src/com/android/launcher3/widget/BaseWidgetSheet.java
@@ -198,7 +198,9 @@
     /** Returns the number of cells that can fit horizontally in a given {@code content}. */
     protected int computeMaxHorizontalSpans(View content, int contentHorizontalPaddingPx) {
         DeviceProfile deviceProfile = mActivityContext.getDeviceProfile();
-        int availableWidth = content.getMeasuredWidth() - contentHorizontalPaddingPx;
+        int availableWidth = content.getMeasuredWidth()
+                - contentHorizontalPaddingPx
+                - (2 * mContentHorizontalMarginInPx);
         Point cellSize = deviceProfile.getCellSize();
         if (cellSize.x > 0) {
             return availableWidth / cellSize.x;