Tab Search: Enable feedback button for Desktop platforms

This CL adds support for the feedback button on non ChromeOS desktop
platforms Windows, Mac and Linux.

See below for details on new feedback bucket.
https://docs.google.com/document/d/1vepB7t_cYatX_-jNkVbkv49WSVPCk80ueHlg7oW6TIA/edit

Bug: 1099917
Change-Id: I795ac19fe9e4fb5b8655c721ca9bf62b9728f992
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2523489Reviewed-by: Roman Arora <romanarora@chromium.org>
Commit-Queue: Thomas Lukaszewicz <tluk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#825073}

chrome/browser/ui/webui/tab_search/tab_search_page_handler.cc

@@ -29,6 +29,12 @@
 namespace {
 constexpr base::TimeDelta kTabsChangeDelay =
     base::TimeDelta::FromMilliseconds(50);
+
+#if defined(OS_CHROMEOS)
+constexpr char kFeedbackCategoryTag[] = "FromTabSearch";
+#else
+constexpr char kFeedbackCategoryTag[] = "FromTabSearchBrowser";
+#endif
 }
 
 TabSearchPageHandler::TabSearchPageHandler(
@@ -137,7 +143,7 @@ void TabSearchPageHandler::ShowFeedbackPage() {
                            chrome::FeedbackSource::kFeedbackSourceTabSearch,
                            std::string() /* description_template */,
                            std::string() /* description_placeholder_text */,
-                           std::string("FromTabSearch") /* category_tag */,
+                           std::string(kFeedbackCategoryTag) /* category_tag */,
                            std::string() /* extra_diagnostics */);
 }