IndexedDB: Create IDBTransaction interface

This CL creates a bare IDBTransaction interface with just the
CreateObjectStore method.  Later CLs will be responsible for
moving the remaining methods from IDBDatabase to IDBTransaction.

Bug: 717812
Change-Id: Ie1e084957e66f2afef563d37af9243726e48855b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1526172
Reviewed-by: Kinuko Yasuda <[email protected]>
Reviewed-by: Tom Sepez <[email protected]>
Reviewed-by: Daniel Murphy <[email protected]>
Commit-Queue: Chase Phillips <[email protected]>
Cr-Commit-Position: refs/heads/master@{#643406}
diff --git a/content/browser/BUILD.gn b/content/browser/BUILD.gn
index 49ab076..faf64e2 100644
--- a/content/browser/BUILD.gn
+++ b/content/browser/BUILD.gn
@@ -1056,6 +1056,8 @@
     "indexed_db/scopes/scope_lock_range.h",
     "indexed_db/scopes/scopes_lock_manager.cc",
     "indexed_db/scopes/scopes_lock_manager.h",
+    "indexed_db/transaction_impl.cc",
+    "indexed_db/transaction_impl.h",
     "initiator_csp_context.cc",
     "initiator_csp_context.h",
     "installedapp/installed_app_provider_impl_default.cc",