Removes unnecessary width/height

Resolves #7403 #7662

Auditors: @bsclifton

Test Plan:
- specified in the issue #7403

js/components/contextMenu.js

@@ -94,7 +94,7 @@ class ContextMenuItem extends ImmutableComponent {
       const parentBoundingRect = parentNode.getBoundingClientRect()
       const boundingRect = node.getBoundingClientRect()
       openedSubmenuDetails = openedSubmenuDetails.push(Immutable.fromJS({
-        y: boundingRect.top - parentBoundingRect.top - 1,
+        y: boundingRect.top - parentBoundingRect.top - 1 + parentNode.scrollTop,
         template: this.submenu
       }))
     }
@@ -218,7 +218,7 @@ class ContextMenuSingle extends ImmutableComponent {
   render () {
     const styles = {}
     if (this.props.y) {
-      styles.top = this.props.y
+      styles.marginTop = this.props.y
     }
     const visibleMenuItems = this.props.template.filter((element) => {
       return element.has('visible')
@@ -443,7 +443,7 @@ class ContextMenu extends ImmutableComponent {
       styles.right = this.props.contextMenuDetail.get('right')
     }
     if (this.props.contextMenuDetail.get('top') !== undefined) {
-      styles.top = this.props.contextMenuDetail.get('top')
+      styles.marginTop = this.props.contextMenuDetail.get('top')
     }
     if (this.props.contextMenuDetail.get('bottom') !== undefined) {
       styles.bottom = this.props.contextMenuDetail.get('bottom')

less/contextMenu.less

@@ -20,16 +20,19 @@
   }
   // This is a reasonable max height and also solves problems for bookmarks menu
   // and bookmarks overflow menu reaching down too low.
-  height: 100%;
-  width: 100%;
+  min-width: 225px;
   @usedUpChrome: @navbarHeight + @bookmarksToolbarWithFaviconsHeight;
   max-height: calc(~'100% - @{usedUpChrome}');
   overflow: auto;
   position: absolute;
   z-index: @zindexContextMenu;
+  padding-right: 10px;
+  padding-bottom: 10px;
   -webkit-user-select: none;
   &.reverseExpand {
     flex-direction: row-reverse;
+    padding-right: 0;
+    padding-left: 10px;
   }
 
   .contextMenuSingle {