sessions: moves SessionTabHelper to components/sessions

This way WebLayer can use it.

ENABLE_SESSION_SERVICE case is handled in chrome side by supplying
a null SessionService if ENABLE_SESSION_SERVICE is false.

BUG=1033924
TEST=none

Change-Id: I334274270d3e06e829d6f67e132467f0f8b9c73d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1999152
Commit-Queue: Scott Violet <[email protected]>
Reviewed-by: Reilly Grant <[email protected]>
Reviewed-by: Evan Stade <[email protected]>
Cr-Commit-Position: refs/heads/master@{#731620}
diff --git a/chrome/browser/ui/sync/browser_synced_tab_delegate.cc b/chrome/browser/ui/sync/browser_synced_tab_delegate.cc
index e003a56..5b529cdc0 100644
--- a/chrome/browser/ui/sync/browser_synced_tab_delegate.cc
+++ b/chrome/browser/ui/sync/browser_synced_tab_delegate.cc
@@ -4,8 +4,8 @@
 
 #include "chrome/browser/ui/sync/browser_synced_tab_delegate.h"
 
-#include "chrome/browser/sessions/session_tab_helper.h"
 #include "chrome/browser/sync/sessions/sync_sessions_router_tab_helper.h"
+#include "components/sessions/content/session_tab_helper.h"
 
 BrowserSyncedTabDelegate::BrowserSyncedTabDelegate(
     content::WebContents* web_contents) {
@@ -15,11 +15,13 @@
 BrowserSyncedTabDelegate::~BrowserSyncedTabDelegate() {}
 
 SessionID BrowserSyncedTabDelegate::GetWindowId() const {
-  return SessionTabHelper::FromWebContents(web_contents())->window_id();
+  return sessions::SessionTabHelper::FromWebContents(web_contents())
+      ->window_id();
 }
 
 SessionID BrowserSyncedTabDelegate::GetSessionId() const {
-  return SessionTabHelper::FromWebContents(web_contents())->session_id();
+  return sessions::SessionTabHelper::FromWebContents(web_contents())
+      ->session_id();
 }
 
 bool BrowserSyncedTabDelegate::IsPlaceholderTab() const {