PDF Viewer: Small cleanup in updateUIForViewportChange().

Delegate more logic from pdf-viewer into viewer-zoom-toolbar.

Bug: None
Change-Id: I4a80f895ce26825dc491cd7eb4291afdc4b5292f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2285360Reviewed-by: Rebekah Potter <rbpotter@chromium.org>
Commit-Queue: dpapad <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#786546}

chrome/browser/resources/pdf/elements/BUILD.gn

@@ -116,6 +116,7 @@ js_library("viewer-zoom-toolbar") {
     ":viewer-zoom-button",
     "..:constants",
     "//ui/webui/resources/js:assert.m",
+    "//ui/webui/resources/js:util.m",
   ]
 }
 

chrome/browser/resources/pdf/elements/viewer-zoom-toolbar.js

@@ -9,6 +9,7 @@ import './viewer-zoom-button.js';
 
 import {assert} from 'chrome://resources/js/assert.m.js';
 import {loadTimeData} from 'chrome://resources/js/load_time_data.m.js';
+import {isRTL} from 'chrome://resources/js/util.m.js';
 import {html, Polymer} from 'chrome://resources/polymer/v3_0/polymer/polymer_bundled.min.js';
 
 import {FittingType} from '../constants.js';
@@ -161,4 +162,31 @@ Polymer({
       this.$['zoom-out-button'].hide();
     }
   },
+
+  /**
+   * Offsets the toolbar position so that it doesn't move if scrollbars appear.
+   * @param {!{horizontal: boolean, vertical: boolean}} hasScrollbars
+   * @param {number} scrollbarWidth
+   */
+  shiftForScrollbars(hasScrollbars, scrollbarWidth) {
+    const verticalScrollbarWidth = hasScrollbars.vertical ? scrollbarWidth : 0;
+    const horizontalScrollbarWidth =
+        hasScrollbars.horizontal ? scrollbarWidth : 0;
+
+    // Shift the zoom toolbar to the left by half a scrollbar width. This
+    // gives a compromise: if there is no scrollbar visible then the toolbar
+    // will be half a scrollbar width further left than the spec but if there
+    // is a scrollbar visible it will be half a scrollbar width further right
+    // than the spec. In RTL layout normally, the zoom toolbar is on the left
+    // left side, but the scrollbar is still on the right, so this is not
+    // necessary.
+    if (!isRTL()) {
+      this.style.right = -verticalScrollbarWidth + (scrollbarWidth / 2) + 'px';
+    }
+    // Having a horizontal scrollbar is much rarer so we don't offset the
+    // toolbar from the bottom any more than what the spec says. This means
+    // that when there is a scrollbar visible, it will be a full scrollbar
+    // width closer to the bottom of the screen than usual, but this is ok.
+    this.style.bottom = -horizontalScrollbarWidth + 'px';
+  }
 });

chrome/browser/resources/pdf/pdf_viewer.js

@@ -15,7 +15,7 @@ import './pdf_viewer_shared_style.js';
 
 import {assert, assertNotReached} from 'chrome://resources/js/assert.m.js';
 import {loadTimeData} from 'chrome://resources/js/load_time_data.m.js';
-import {hasKeyModifiers, isRTL} from 'chrome://resources/js/util.m.js';
+import {hasKeyModifiers} from 'chrome://resources/js/util.m.js';
 import {html} from 'chrome://resources/polymer/v3_0/polymer/polymer_bundled.min.js';
 
 import {Bookmark} from './bookmark_type.js';
@@ -596,31 +596,9 @@ class PDFViewerElement extends PDFViewerBaseElement {
 
   /** @override */
   updateUIForViewportChange() {
-    // Offset the toolbar position so that it doesn't move if scrollbars appear.
-    const hasScrollbars = this.viewport.documentHasScrollbars();
-    const scrollbarWidth = this.viewport.scrollbarWidth;
-    const verticalScrollbarWidth = hasScrollbars.vertical ? scrollbarWidth : 0;
-    const horizontalScrollbarWidth =
-        hasScrollbars.horizontal ? scrollbarWidth : 0;
-
     if (!this.pdfViewerUpdateEnabled_) {
-      // Shift the zoom toolbar to the left by half a scrollbar width. This
-      // gives a compromise: if there is no scrollbar visible then the toolbar
-      // will be half a scrollbar width further left than the spec but if there
-      // is a scrollbar visible it will be half a scrollbar width further right
-      // than the spec. In RTL layout normally, the zoom toolbar is on the left
-      // left side, but the scrollbar is still on the right, so this is not
-      // necessary.
-      const zoomToolbar = this.getZoomToolbar_();
-      if (!isRTL()) {
-        zoomToolbar.style.right =
-            -verticalScrollbarWidth + (scrollbarWidth / 2) + 'px';
-      }
-      // Having a horizontal scrollbar is much rarer so we don't offset the
-      // toolbar from the bottom any more than what the spec says. This means
-      // that when there is a scrollbar visible, it will be a full scrollbar
-      // width closer to the bottom of the screen than usual, but this is ok.
-      zoomToolbar.style.bottom = -horizontalScrollbarWidth + 'px';
+      this.getZoomToolbar_().shiftForScrollbars(
+          this.viewport.documentHasScrollbars(), this.viewport.scrollbarWidth);
     }
 
     // Update the page indicator.