indexeddb: Make IndexedDBContextImpl::data_path_ constant.

Make IndexedDBContextImpl::data_path_ a constant member as it is
never changed. Doing so makes it easier to reason about safe
access on different sequences. set_data_path_for_testing() existed,
and was used by IndexedDBQuotaClientTest, but was only ever set to
the same path passed to the IndexedDBContextImpl constructor.

Also make IndexedDBContextImpl::data_path() return a const reference
to avoid unnecessary creation of intermediate base::FilePath
instances.

Bug: none
Change-Id: If7c5a960c30dd7d4858fd332437548d7363247d1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2606651Reviewed-by: Daniel Murphy <dmurph@chromium.org>
Commit-Queue: Chris Mumford <cmumford@google.com>
Cr-Commit-Position: refs/heads/master@{#839666}

content/browser/indexed_db/indexed_db_context_impl.cc

@@ -135,13 +135,13 @@ IndexedDBContextImpl::IndexedDBContextImpl(
                      // BLOCK_SHUTDOWN to support clearing session-only storage.
                      base::TaskShutdownBehavior::BLOCK_SHUTDOWN}))),
       dispatcher_host_(this, std::move(io_task_runner)),
+      data_path_(data_path.empty() ? base::FilePath()
+                                   : data_path.Append(kIndexedDBDirectory)),
       force_keep_session_state_(false),
       quota_manager_proxy_(quota_manager_proxy),
       clock_(clock),
       filesystem_proxy_(storage::CreateFilesystemProxy()) {
   IDB_TRACE("init");
-  if (!data_path.empty())
-    data_path_ = data_path.Append(kIndexedDBDirectory);
   quota_manager_proxy->RegisterClient(
       base::MakeRefCounted<IndexedDBQuotaClient>(this),
       storage::QuotaClientType::kIndexedDatabase,

content/browser/indexed_db/indexed_db_context_impl.h

@@ -178,16 +178,11 @@ class CONTENT_EXPORT IndexedDBContextImpl
   // order.
   std::vector<base::FilePath> GetStoragePaths(const url::Origin& origin) const;
 
-  base::FilePath data_path() const { return data_path_; }
+  const base::FilePath& data_path() const { return data_path_; }
   bool IsInMemoryContext() const { return data_path_.empty(); }
   size_t GetConnectionCountSync(const url::Origin& origin);
   int GetOriginBlobFileCount(const url::Origin& origin);
 
-  // For unit tests allow to override the |data_path_|.
-  void set_data_path_for_testing(const base::FilePath& data_path) {
-    data_path_ = data_path;
-  }
-
   bool is_incognito() const { return data_path_.empty(); }
 
   storage::mojom::BlobStorageContext* blob_storage_context() const {
@@ -246,7 +241,7 @@ class CONTENT_EXPORT IndexedDBContextImpl
 
   // If |data_path_| is empty then this is an incognito session and the backing
   // store will be held in-memory rather than on-disk.
-  base::FilePath data_path_;
+  const base::FilePath data_path_;
 
   // If true, nothing (not even session-only data) should be deleted on exit.
   bool force_keep_session_state_;

content/browser/indexed_db/indexed_db_quota_client_unittest.cc

@@ -67,10 +67,7 @@ class IndexedDBQuotaClientTest : public testing::Test {
   void CreateTempDir() { ASSERT_TRUE(temp_dir_.CreateUniqueTempDir()); }
 
   void SetupTempDir() {
-    base::FilePath indexeddb_dir =
-        temp_dir_.GetPath().Append(IndexedDBContextImpl::kIndexedDBDirectory);
-    ASSERT_TRUE(base::CreateDirectory(indexeddb_dir));
-    idb_context()->set_data_path_for_testing(indexeddb_dir);
+    ASSERT_TRUE(base::CreateDirectory(idb_context_->data_path()));
   }
 
   ~IndexedDBQuotaClientTest() override {