[Mac][Material Design] Use white tab spinner for dark themes.

chrome/browser/ui/cocoa/tabs/tab_strip_controller.mm

Index: chrome/browser/ui/cocoa/tabs/tab_strip_controller.mm
diff --git a/chrome/browser/ui/cocoa/tabs/tab_strip_controller.mm b/chrome/browser/ui/cocoa/tabs/tab_strip_controller.mm
index 511ad7e3402526b67da908d231718503fd3aab53..3f27d14469dc5872ac4d4d9e20d6252bdd88968a 100644
--- a/chrome/browser/ui/cocoa/tabs/tab_strip_controller.mm
+++ b/chrome/browser/ui/cocoa/tabs/tab_strip_controller.mm
@@ -1564,7 +1564,7 @@ private:
   } else if (contents->IsWaitingForResponse()) {
     newState = kTabWaiting;
     if (ui::MaterialDesignController::IsModeMaterial() &&
-        [[[tabController view] window] inIncognitoMode]) {
+        [[[tabController view] window] hasDarkTheme]) {
       throbberImage = throbberWaitingIncognitoImage;
     } else {
       throbberImage = throbberWaitingImage;
@@ -1572,7 +1572,7 @@ private:
   } else if (contents->IsLoadingToDifferentDocument()) {
     newState = kTabLoading;
     if (ui::MaterialDesignController::IsModeMaterial() &&
-        [[[tabController view] window] inIncognitoMode]) {
+        [[[tabController view] window] hasDarkTheme]) {
       throbberImage = throbberLoadingIncognitoImage;
     } else {
       throbberImage = throbberLoadingImage;