remove mItemDividerHeight from app menu

This is different from current app menu redesign divider lines.
AppMenu#mItemDividerHeight added long time ago, from the screenshot in
crbug.com/331960,it seems app menu had divider lines between each items.
And mItemDividerHeight is for calculate the height for that divider
lines.

And from https://codereview.chromium.org/377083002, we start to use
OverflowMenuTheme in styles.xml(now it named OverflowMenuThemeOverlay),
and it set <item name="android:listDivider">@null</item>, so we are no
longer need AppMenu#mItemDividerHeight.

Change-Id: I8c6bf1a5c9aeb5b5ac82eda7c6a5e924c7432156
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2393523Reviewed-by: Theresa  <twellington@chromium.org>
Commit-Queue: Gang Wu <gangwu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#805095}

chrome/browser/ui/android/appmenu/internal/java/src/org/chromium/chrome/browser/ui/appmenu/AppMenu.java

@@ -57,7 +57,6 @@ class AppMenu implements OnItemClickListener, OnKeyListener, AppMenuAdapter.OnCl
 
     private final Menu mMenu;
     private final int mItemRowHeight;
-    private final int mItemDividerHeight;
     private final int mVerticalFadeDistance;
     private final int mNegativeSoftwareVerticalOffset;
     private final int mNegativeVerticalOffsetNotTopAnchored;
@@ -79,13 +78,12 @@ class AppMenu implements OnItemClickListener, OnKeyListener, AppMenuAdapter.OnCl
      * Creates and sets up the App Menu.
      * @param menu Original menu created by the framework.
      * @param itemRowHeight Desired height for each app menu row.
-     * @param itemDividerHeight Desired height for the divider between app menu items.
      * @param handler AppMenuHandlerImpl receives callbacks from AppMenu.
      * @param res Resources object used to get dimensions and style attributes.
      * @param iconBeforeItem Whether icon is shown before the text.
      */
-    AppMenu(Menu menu, int itemRowHeight, int itemDividerHeight, AppMenuHandlerImpl handler,
-            Resources res, boolean iconBeforeItem) {
+    AppMenu(Menu menu, int itemRowHeight, AppMenuHandlerImpl handler, Resources res,
+            boolean iconBeforeItem) {
         mMenu = menu;
 
         mItemRowHeight = itemRowHeight;
@@ -93,9 +91,6 @@ class AppMenu implements OnItemClickListener, OnKeyListener, AppMenuAdapter.OnCl
 
         mHandler = handler;
 
-        mItemDividerHeight = itemDividerHeight;
-        assert mItemDividerHeight >= 0;
-
         mNegativeSoftwareVerticalOffset =
                 res.getDimensionPixelSize(R.dimen.menu_negative_software_vertical_offset);
         mVerticalFadeDistance = res.getDimensionPixelSize(R.dimen.menu_vertical_fade_distance);

chrome/browser/ui/android/appmenu/internal/java/src/org/chromium/chrome/browser/ui/appmenu/AppMenuHandlerImpl.java

@@ -188,14 +188,14 @@ class AppMenuHandlerImpl
                 new ContextThemeWrapper(context, R.style.OverflowMenuThemeOverlay);
 
         if (mAppMenu == null) {
-            TypedArray a = wrapper.obtainStyledAttributes(new int[] {
-                    android.R.attr.listPreferredItemHeightSmall, android.R.attr.listDivider});
+            TypedArray a = wrapper.obtainStyledAttributes(
+                    new int[] {android.R.attr.listPreferredItemHeightSmall});
             int itemRowHeight = a.getDimensionPixelSize(0, 0);
             Drawable itemDivider = a.getDrawable(1);
             int itemDividerHeight = itemDivider != null ? itemDivider.getIntrinsicHeight() : 0;
             a.recycle();
-            mAppMenu = new AppMenu(mMenu, itemRowHeight, itemDividerHeight, this,
-                    context.getResources(), mDelegate.shouldShowIconBeforeItem());
+            mAppMenu = new AppMenu(mMenu, itemRowHeight, this, context.getResources(),
+                    mDelegate.shouldShowIconBeforeItem());
             mAppMenuDragHelper = new AppMenuDragHelper(context, mAppMenu, itemRowHeight);
         }