Remove an incorrect DCHECK in GeneratedCodeCache

The DCHECK in IssuePendingOperations is not correct. We still need
to issue pending operations when the backend has failed so we can call
required callbacks (for ex: for FetchEntry requests). This DCHECK was
added in an older version of code when we didn't receive any requests
before initializing the backend.

Also adds a test to test this path.

Change-Id: I5eec4886445eb65b0b083cc0805713449d07fc11
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1634703Reviewed-by: Maks Orlovich <morlovich@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Mythri Alle <mythria@chromium.org>
Cr-Commit-Position: refs/heads/master@{#664693}

content/browser/code_cache/generated_code_cache.cc

@@ -336,7 +336,6 @@ void GeneratedCodeCache::DidCreateBackend(
 }
 
 void GeneratedCodeCache::IssuePendingOperations() {
-  DCHECK_EQ(backend_state_, kInitialized);
   // Issue all the pending operations that were received when creating
   // the backend.
   for (auto const& op : pending_ops_) {

content/browser/code_cache/generated_code_cache_unittest.cc

@@ -367,4 +367,20 @@ TEST_F(GeneratedCodeCacheTest, WasmCache) {
   ASSERT_TRUE(received_);
   EXPECT_EQ(kInitialData, received_data_);
 }
+
+TEST_F(GeneratedCodeCacheTest, TestFailedBackendOpening) {
+  GURL url(kInitialUrl);
+  GURL origin_lock = GURL(kInitialOrigin);
+
+  // Clear cache_path_ so the backend initialization fails.
+  cache_path_.clear();
+  InitializeCacheAndReOpen(GeneratedCodeCache::CodeCacheType::kJavaScript);
+  FetchFromCache(url, origin_lock);
+  scoped_task_environment_.RunUntilIdle();
+
+  // We should still receive a callback.
+  ASSERT_TRUE(received_);
+  // We shouldn't receive any data.
+  ASSERT_TRUE(received_null_);
+}
 }  // namespace content