Add side-panel prototype using read later

Bug: 1141224
Change-Id: Id2ff6354f5f8f7e29c7e20f1b27ee7fb10989386
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2481833
Auto-Submit: Peter Boström <[email protected]>
Commit-Queue: Thomas Lukaszewicz <[email protected]>
Reviewed-by: Thomas Lukaszewicz <[email protected]>
Cr-Commit-Position: refs/heads/master@{#820039}
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index 35ba25f..3a37450 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -4308,6 +4308,10 @@
      flag_descriptions::kScrollableTabStripDescription, kOsDesktop,
      FEATURE_VALUE_TYPE(features::kScrollableTabStrip)},
 
+    {"side-panel", flag_descriptions::kSidePanelName,
+     flag_descriptions::kSidePanelDescription, kOsDesktop,
+     FEATURE_VALUE_TYPE(features::kSidePanel)},
+
     {"tab-outlines-in-low-contrast-themes",
      flag_descriptions::kTabOutlinesInLowContrastThemesName,
      flag_descriptions::kTabOutlinesInLowContrastThemesDescription, kOsDesktop,