Remove the PDFSinglePageViewer-specific code from web/secondary_toolbar.js (PR 9877 follow-up)

This was added on the assumption that the viewer would (eventually) start using the `PDFSinglePageViewer` for e.g. PAGE-scrolling mode and PresentationMode. However, having both a `PDFViewer` and a `PDFSinglePageViewer` side-by-side in the viewer would've been tricky to implement well, which is why PR 14112 implemented PAGE-scrolling for the general `BaseViewer` instead.

Given that the default viewer is no longer (potentially) going to use `PDFSinglePageViewer`, there's code in the `SecondaryToolbar` (and related CSS rules) which is now unnecessary.

web/secondary_toolbar.js

@@ -15,7 +15,6 @@
 
 import { SCROLLBAR_PADDING, ScrollMode, SpreadMode } from "./ui_utils.js";
 import { CursorTool } from "./pdf_cursor_tools.js";
-import { PDFSinglePageViewer } from "./pdf_viewer.js";
 
 /**
  * @typedef {Object} SecondaryToolbarOptions
@@ -166,22 +165,6 @@ class SecondaryToolbar {
 
     // Bind the event listener for adjusting the 'max-height' of the toolbar.
     this.eventBus._on("resize", this._setMaxHeight.bind(this));
-
-    // Hide the Scroll/Spread mode buttons, when they're not applicable to the
-    // current `BaseViewer` instance (in particular `PDFSinglePageViewer`).
-    this.eventBus._on("baseviewerinit", evt => {
-      if (evt.source instanceof PDFSinglePageViewer) {
-        this.toolbarButtonContainer.classList.add(
-          "hiddenScrollModeButtons",
-          "hiddenSpreadModeButtons"
-        );
-      } else {
-        this.toolbarButtonContainer.classList.remove(
-          "hiddenScrollModeButtons",
-          "hiddenSpreadModeButtons"
-        );
-      }
-    });
   }
 
   /**

web/viewer.css

@@ -625,11 +625,6 @@ html[dir="rtl"] .secondaryToolbar {
   margin-bottom: -4px;
 }
 
-#secondaryToolbarButtonContainer.hiddenScrollModeButtons > .scrollModeButtons,
-#secondaryToolbarButtonContainer.hiddenSpreadModeButtons > .spreadModeButtons {
-  display: none !important;
-}
-
 .doorHanger,
 .doorHangerRight {
   border-radius: 2px;

web/viewer.html

@@ -196,32 +196,32 @@ See https://github.com/adobe-type-tools/cmap-resources
 
             <div class="horizontalToolbarSeparator"></div>
 
-            <button id="scrollPage" class="secondaryToolbarButton scrollModeButtons scrollPage" title="Use Page Scrolling" tabindex="62" data-l10n-id="scroll_page">
+            <button id="scrollPage" class="secondaryToolbarButton scrollPage" title="Use Page Scrolling" tabindex="62" data-l10n-id="scroll_page">
               <span data-l10n-id="scroll_page_label">Page Scrolling</span>
             </button>
-            <button id="scrollVertical" class="secondaryToolbarButton scrollModeButtons scrollVertical toggled" title="Use Vertical Scrolling" tabindex="63" data-l10n-id="scroll_vertical">
+            <button id="scrollVertical" class="secondaryToolbarButton scrollVertical toggled" title="Use Vertical Scrolling" tabindex="63" data-l10n-id="scroll_vertical">
               <span data-l10n-id="scroll_vertical_label">Vertical Scrolling</span>
             </button>
-            <button id="scrollHorizontal" class="secondaryToolbarButton scrollModeButtons scrollHorizontal" title="Use Horizontal Scrolling" tabindex="64" data-l10n-id="scroll_horizontal">
+            <button id="scrollHorizontal" class="secondaryToolbarButton scrollHorizontal" title="Use Horizontal Scrolling" tabindex="64" data-l10n-id="scroll_horizontal">
               <span data-l10n-id="scroll_horizontal_label">Horizontal Scrolling</span>
             </button>
-            <button id="scrollWrapped" class="secondaryToolbarButton scrollModeButtons scrollWrapped" title="Use Wrapped Scrolling" tabindex="65" data-l10n-id="scroll_wrapped">
+            <button id="scrollWrapped" class="secondaryToolbarButton scrollWrapped" title="Use Wrapped Scrolling" tabindex="65" data-l10n-id="scroll_wrapped">
               <span data-l10n-id="scroll_wrapped_label">Wrapped Scrolling</span>
             </button>
 
-            <div class="horizontalToolbarSeparator scrollModeButtons"></div>
+            <div class="horizontalToolbarSeparator"></div>
 
-            <button id="spreadNone" class="secondaryToolbarButton spreadModeButtons spreadNone toggled" title="Do not join page spreads" tabindex="66" data-l10n-id="spread_none">
+            <button id="spreadNone" class="secondaryToolbarButton spreadNone toggled" title="Do not join page spreads" tabindex="66" data-l10n-id="spread_none">
               <span data-l10n-id="spread_none_label">No Spreads</span>
             </button>
-            <button id="spreadOdd" class="secondaryToolbarButton spreadModeButtons spreadOdd" title="Join page spreads starting with odd-numbered pages" tabindex="67" data-l10n-id="spread_odd">
+            <button id="spreadOdd" class="secondaryToolbarButton spreadOdd" title="Join page spreads starting with odd-numbered pages" tabindex="67" data-l10n-id="spread_odd">
               <span data-l10n-id="spread_odd_label">Odd Spreads</span>
             </button>
-            <button id="spreadEven" class="secondaryToolbarButton spreadModeButtons spreadEven" title="Join page spreads starting with even-numbered pages" tabindex="68" data-l10n-id="spread_even">
+            <button id="spreadEven" class="secondaryToolbarButton spreadEven" title="Join page spreads starting with even-numbered pages" tabindex="68" data-l10n-id="spread_even">
               <span data-l10n-id="spread_even_label">Even Spreads</span>
             </button>
 
-            <div class="horizontalToolbarSeparator spreadModeButtons"></div>
+            <div class="horizontalToolbarSeparator"></div>
 
             <button id="documentProperties" class="secondaryToolbarButton documentProperties" title="Document Properties…" tabindex="69" data-l10n-id="document_properties">
               <span data-l10n-id="document_properties_label">Document Properties…</span>