Print Preview: Fix cursor on custom margins textboxes

The resize cursor should only appear within 8px of the lines, not on or
near the textboxes.

Bug: 980442
Change-Id: I63dc48bcdd48bae7d484584078189f0b9739a1bb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1689343Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Commit-Queue: Rebekah Potter <rbpotter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#675745}

chrome/browser/resources/print_preview/ui/margin_control.html

@@ -29,15 +29,15 @@
         pointer-events: none;
       }
 
-      :host([side=top]),
-      :host([side=bottom]) {
+      :host([side=top]) #lineContainer,
+      :host([side=bottom]) #lineContainer {
         cursor: ns-resize;
         padding: 8px 0;
         width: 100%;
       }
 
-      :host([side=left]),
-      :host([side=right]) {
+      :host([side=left]) #lineContainer,
+      :host([side=right]) #lineContainer {
         cursor: ew-resize;
         height: 100%;
         padding: 0 8px;
@@ -146,7 +146,9 @@
         padding-inline-end: 8px;
       }
     </style>
-      <div id="line"></div>
+      <div id="lineContainer">
+        <div id="line"></div>
+      </div>
       <div id="row-container">
         <div id="input-container">
           <input id="input" disabled="[[disabled]]" aria-label$="[[i18n(side)]]"

chrome/browser/resources/print_preview/ui/margin_control.js

@@ -164,7 +164,7 @@ Polymer({
    */
   shouldDrag: function(event) {
     return !this.disabled && event.button == 0 &&
-        (event.path[0] == this || event.path[0] == this.$.line);
+        (event.path[0] == this.$.lineContainer || event.path[0] == this.$.line);
   },
 
   /** @private */