DevTools: Localize two strings for the checkboxes in Layers panel.

Two strings for the checkboxes in Layers panel are not localized. This CL
wrap them with ls, and include the strings in the GRDP.
https://imgur.com/fbrbvKY

Bug: 941561
Change-Id: Iab4e3bfaa791dbb9542133109367284465b59d98
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1779170Reviewed-by: Erik Luo <luoe@chromium.org>
Commit-Queue: Christy Chen <chrche@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#695240}

third_party/blink/renderer/devtools/front_end/layer_viewer/Layers3DView.js

@@ -678,10 +678,10 @@ LayerViewer.Layers3DView = class extends UI.VBox {
   _initToolbar() {
     this._panelToolbar = this._transformController.toolbar();
     this.contentElement.appendChild(this._panelToolbar.element);
-    this._showSlowScrollRectsSetting =
-        this._createVisibilitySetting('Slow scroll rects', 'frameViewerShowSlowScrollRects', true, this._panelToolbar);
+    this._showSlowScrollRectsSetting = this._createVisibilitySetting(
+        ls`Slow scroll rects`, 'frameViewerShowSlowScrollRects', true, this._panelToolbar);
     this._showPaintsSetting =
-        this._createVisibilitySetting('Paints', 'frameViewerShowPaints', true, this._panelToolbar);
+        this._createVisibilitySetting(ls`Paints`, 'frameViewerShowPaints', true, this._panelToolbar);
     this._showPaintsSetting.addChangeListener(this._updatePaints, this);
     Common.moduleSetting('frameViewerHideChromeWindow').addChangeListener(this._update, this);
   }

third_party/blink/renderer/devtools/front_end/layer_viewer/layer_viewer_strings.grdp

@@ -210,4 +210,10 @@
   <message name="IDS_DEVTOOLS_fd63c694ddc8073cf10bb8025aa9aaaf" desc="Text in Layer Details View of the Layers panel">
     Layer for scrollbar.
   </message>
+  <message name="IDS_DEVTOOLS_a3ed19b48390aad906de764e0476142d" desc="Text for a checkbox in the toolbar of the Layers panel to show the paints of the page">
+    Paints
+  </message>
+  <message name="IDS_DEVTOOLS_4f6faa156251f75fbefe3270d94a7a28" desc="Text for a checkbox in the toolbar of the Layers panel to show the area of slow scroll rect">
+    Slow scroll rects
+  </message>
 </grit-part>
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