Added --enable-ui-devtools to chrome://flags.

chrome/browser/about_flags.cc

Index: chrome/browser/about_flags.cc
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index 64b0bb2f51e338e3e2cfb509d9a86bc35f038403..3e72025c25b3eaa7f08f159352f9eb58a275a620 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -115,6 +115,7 @@
 #if defined(OS_CHROMEOS)
 #include "chromeos/chromeos_switches.h"
 #include "components/arc/arc_features.h"
+#include "components/ui_devtools/switches.h"
 #include "third_party/cros_system_api/switches/chrome_switches.h"
 #endif  // OS_CHROMEOS
 
@@ -2734,6 +2735,13 @@ const FeatureEntry kFeatureEntries[] = {
          // when the flag is manually enabled in a local build.
          "AutofillCreditCardDropdownVariations")},
 #endif  // OS_ANDROID
+
+#if defined(OS_CHROMEOS)
+    {ui::devtools::kEnableUiDevTools, flag_descriptions::kUiDevToolsName,
+     flag_descriptions::kUiDevToolsDescription, kOsCrOS,
+     SINGLE_VALUE_TYPE(ui::devtools::kEnableUiDevTools)},
+#endif  // defined(OS_CHROMEOS)
+
     {"enable-autofill-credit-card-last-used-date-display",
      flag_descriptions::kEnableAutofillCreditCardLastUsedDateDisplayName,
      flag_descriptions::kEnableAutofillCreditCardLastUsedDateDisplayDescription,
@@ -3115,6 +3123,12 @@ bool SkipConditionalFeatureEntry(const FeatureEntry& entry) {
       channel != version_info::Channel::UNKNOWN) {
     return true;
   }
+
+  // enable-ui-devtools is only available on for non Stable channels.
+  if (!strcmp(ui::devtools::kEnableUiDevTools, entry.internal_name) &&
+      channel == version_info::Channel::STABLE) {
+    return true;
+  }
 #endif  // defined(OS_CHROMEOS)
 
   // data-reduction-proxy-lo-fi and enable-data-reduction-proxy-lite-page