IndexedDB: Fixed support for empty blobs.

This solution allows empty blobs (and files) to be created.
Most tests for this change are Blink layout tests, so will land
in a separate CL.

BUG=399323

Review URL: https://codereview.chromium.org/942633004

Cr-Commit-Position: refs/heads/master@{#320636}

4 files changed, 72 insertions, 2 deletions

diff --git a/content/browser/indexed_db/indexed_db_backing_store.cc b/content/browser/indexed_db/indexed_db_backing_store.cc
index 4ae9ed4..22bd411 100644
--- a/content/browser/indexed_db/indexed_db_backing_store.cc
+++ b/content/browser/indexed_db/indexed_db_backing_store.cc
@@ -2339,8 +2339,12 @@ class LocalWriteClosure : public FileWriterDelegate::DelegateWriteCallback,
     }
 
     bool success = write_status == FileWriterDelegate::SUCCESS_COMPLETED;
-
-    if (success && !last_modified_.is_null()) {
+    if (success && !bytes_written_) {
+      // LocalFileStreamWriter only creates a file if data is actually written.
+      // If none was then create one now.
+      task_runner_->PostTask(
+          FROM_HERE, base::Bind(&LocalWriteClosure::CreateEmptyFile, this));
+    } else if (success && !last_modified_.is_null()) {
       task_runner_->PostTask(
           FROM_HERE, base::Bind(&LocalWriteClosure::UpdateTimeStamp, this));
     } else {
@@ -2403,6 +2407,20 @@ class LocalWriteClosure : public FileWriterDelegate::DelegateWriteCallback,
     chained_blob_writer_->ReportWriteCompletion(true, bytes_written_);
   }
 
+  // Create an empty file.
+  void CreateEmptyFile() {
+    DCHECK(task_runner_->RunsTasksOnCurrentThread());
+    base::File file(file_path_,
+                    base::File::FLAG_CREATE_ALWAYS | base::File::FLAG_WRITE);
+    bool success = file.created();
+    if (success && !last_modified_.is_null() &&
+        !file.SetTimes(last_modified_, last_modified_)) {
+      // TODO(cmumford): Complain quietly; timestamp's probably not vital.
+    }
+    file.Close();
+    chained_blob_writer_->ReportWriteCompletion(success, bytes_written_);
+  }
+
   scoped_refptr<IndexedDBBackingStore::Transaction::ChainedBlobWriter>
       chained_blob_writer_;
   scoped_refptr<base::SequencedTaskRunner> task_runner_;
diff --git a/content/browser/indexed_db/indexed_db_browsertest.cc b/content/browser/indexed_db/indexed_db_browsertest.cc
index fbe35bf..9bfad25 100644
--- a/content/browser/indexed_db/indexed_db_browsertest.cc
+++ b/content/browser/indexed_db/indexed_db_browsertest.cc
@@ -150,6 +150,22 @@ class IndexedDBBrowserTest : public ContentBrowserTest {
     return disk_usage_;
   }
 
+  virtual int RequestBlobFileCount() {
+    PostTaskAndReplyWithResult(
+        GetContext()->TaskRunner(), FROM_HERE,
+        base::Bind(&IndexedDBContextImpl::GetOriginBlobFileCount, GetContext(),
+                   GURL("file:///")),
+        base::Bind(&IndexedDBBrowserTest::DidGetBlobFileCount, this));
+    scoped_refptr<base::ThreadTestHelper> helper(
+        new base::ThreadTestHelper(BrowserMainLoop::GetInstance()
+                                       ->indexed_db_thread()
+                                       ->message_loop_proxy()));
+    EXPECT_TRUE(helper->Run());
+    // Wait for DidGetBlobFileCount to be called.
+    base::MessageLoop::current()->RunUntilIdle();
+    return blob_file_count_;
+  }
+
  private:
   static MockBrowserTestIndexedDBClassFactory* GetTestClassFactory() {
     static ::base::LazyInstance<MockBrowserTestIndexedDBClassFactory>::Leaky
@@ -165,7 +181,10 @@ class IndexedDBBrowserTest : public ContentBrowserTest {
     disk_usage_ = bytes;
   }
 
+  virtual void DidGetBlobFileCount(int count) { blob_file_count_ = count; }
+
   int64 disk_usage_;
+  int blob_file_count_ = 0;
 
   DISALLOW_COPY_AND_ASSIGN(IndexedDBBrowserTest);
 };
@@ -405,6 +424,25 @@ IN_PROC_BROWSER_TEST_F(IndexedDBBrowserTest, CanDeleteWhenOverQuotaTest) {
   SimpleTest(GetTestUrl("indexeddb", "delete_over_quota.html"));
 }
 
+IN_PROC_BROWSER_TEST_F(IndexedDBBrowserTest, EmptyBlob) {
+  // First delete all IDB's for the test origin
+  GetContext()->TaskRunner()->PostTask(
+      FROM_HERE, base::Bind(&IndexedDBContextImpl::DeleteForOrigin,
+                            GetContext(), GURL("file:///")));
+  EXPECT_EQ(0, RequestBlobFileCount());  // Start with no blob files.
+  const GURL test_url = GetTestUrl("indexeddb", "empty_blob.html");
+  // For some reason Android's futimes fails (EPERM) in this test. Do not assert
+  // file times on Android, but do so on other platforms. crbug.com/467247
+  // TODO(cmumford): Figure out why this is the case and fix if possible.
+#if defined(OS_ANDROID)
+  SimpleTest(GURL(test_url.spec() + "#ignoreTimes"));
+#else
+  SimpleTest(GURL(test_url.spec()));
+#endif
+  // Test stores one blob and one file to disk, so expect two files.
+  EXPECT_EQ(2, RequestBlobFileCount());
+}
+
 IN_PROC_BROWSER_TEST_F(IndexedDBBrowserTestWithGCExposed, BlobDidAck) {
   SimpleTest(GetTestUrl("indexeddb", "blob_did_ack.html"));
   // Wait for idle so that the blob ack has time to be received/processed by
diff --git a/content/browser/indexed_db/indexed_db_context_impl.cc b/content/browser/indexed_db/indexed_db_context_impl.cc
index f1357fd..2a6a4b4 100644
--- a/content/browser/indexed_db/indexed_db_context_impl.cc
+++ b/content/browser/indexed_db/indexed_db_context_impl.cc
@@ -273,6 +273,19 @@ base::ListValue* IndexedDBContextImpl::GetAllOriginsDetails() {
   return list.release();
 }
 
+int IndexedDBContextImpl::GetOriginBlobFileCount(const GURL& origin_url) {
+  DCHECK(TaskRunner()->RunsTasksOnCurrentThread());
+  int count = 0;
+  base::FileEnumerator file_enumerator(
+      GetBlobPath(storage::GetIdentifierFromOrigin(origin_url)), true,
+      base::FileEnumerator::FILES);
+  for (base::FilePath file_path = file_enumerator.Next(); !file_path.empty();
+       file_path = file_enumerator.Next()) {
+    count++;
+  }
+  return count;
+}
+
 int64 IndexedDBContextImpl::GetOriginDiskUsage(const GURL& origin_url) {
   DCHECK(TaskRunner()->RunsTasksOnCurrentThread());
   if (data_path_.empty() || !IsInOriginSet(origin_url))
diff --git a/content/browser/indexed_db/indexed_db_context_impl.h b/content/browser/indexed_db/indexed_db_context_impl.h
index da2878b..2955a3a 100644
--- a/content/browser/indexed_db/indexed_db_context_impl.h
+++ b/content/browser/indexed_db/indexed_db_context_impl.h
@@ -101,6 +101,7 @@ class CONTENT_EXPORT IndexedDBContextImpl
     return set->find(origin_url) != set->end();
   }
   size_t GetConnectionCount(const GURL& origin_url);
+  int GetOriginBlobFileCount(const GURL& origin_url);
 
   // For unit tests allow to override the |data_path_|.
   void set_data_path_for_testing(const base::FilePath& data_path) {