[Sync] Componentize synced_tab_delegate

components/sync_sessions/BUILD.gn

Index: components/sync_sessions/BUILD.gn
diff --git a/components/sync_sessions/BUILD.gn b/components/sync_sessions/BUILD.gn
index 59275aa7da3c6e2100935665e9408ca37ae9d5ba..fdc15e26e117c0d1a987164aeb2d5e5edddfb675 100644
--- a/components/sync_sessions/BUILD.gn
+++ b/components/sync_sessions/BUILD.gn
@@ -17,6 +17,10 @@ source_set("sync_sessions") {
     "revisit/typed_url_page_revisit_observer.h",
     "revisit/typed_url_page_revisit_task.cc",
     "revisit/typed_url_page_revisit_task.h",
+    "sync_sessions_client.cc",
+    "sync_sessions_client.h",
+    "synced_tab_delegate.cc",
+    "synced_tab_delegate.h",
   ]
 
   deps = [
@@ -28,6 +32,20 @@ source_set("sync_sessions") {
   ]
 }
 
+source_set("test_support") {
+  testonly = true
+  sources = [
+    "fake_sync_sessions_client.cc",
+    "fake_sync_sessions_client.h",
+  ]
+
+  public_deps = [
+    ":sync_sessions",
+  ]
+
+  deps = []
+}
+
 source_set("unit_tests") {
   testonly = true
   sources = [
@@ -39,6 +57,7 @@ source_set("unit_tests") {
 
   deps = [
     ":sync_sessions",
+    ":test_support",
     "//base/test:test_support",
     "//testing/gtest",
     "//sync",