Avoid touching extensions::ContentVerifyJob's ref count before it's fully constructed

extensions::ContentVerifyJob is ref counted, and its first reference may
be implicitly created in ContentVerifyJob::Start through base::BindOnce.
However, after an upcoming change to base::Bind, it starts rejecting to
make the implicit first reference to a ref-counted object, as this is
an error prone pattern.

This CL updates callers of ContentVerifyJob::Start to hold to hold the
first reference, before Start() is called.

Bug: 866456
Change-Id: Ib3a70973ac789f60a75e636db03f4e4d66e12603
Reviewed-on: https://chromium-review.googlesource.com/1156704Reviewed-by: Istiaque Ahmed <lazyboy@chromium.org>
Commit-Queue: Taiju Tsuiki <tzik@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579653}

extensions/browser/extension_protocols.cc

@@ -196,7 +196,7 @@ class URLRequestExtensionJob : public net::URLRequestFileJob {
                          const std::string& content_security_policy,
                          bool send_cors_header,
                          bool follow_symlinks_anywhere,
-                         ContentVerifyJob* verify_job)
+                         scoped_refptr<ContentVerifyJob> verify_job)
       : net::URLRequestFileJob(
             request,
             network_delegate,
@@ -204,7 +204,7 @@ class URLRequestExtensionJob : public net::URLRequestFileJob {
             base::CreateTaskRunnerWithTraits(
                 {base::MayBlock(), base::TaskPriority::BEST_EFFORT,
                  base::TaskShutdownBehavior::SKIP_ON_SHUTDOWN})),
-        verify_job_(verify_job),
+        verify_job_(std::move(verify_job)),
         seek_position_(0),
         bytes_read_(0),
         directory_path_(directory_path),
@@ -643,7 +643,7 @@ ExtensionProtocolHandler::MaybeCreateJob(
   if (g_test_handler)
     g_test_handler->Run(&directory_path, &relative_path);
 
-  ContentVerifyJob* verify_job = nullptr;
+  scoped_refptr<ContentVerifyJob> verify_job;
   ContentVerifier* verifier = extension_info_map_->content_verifier();
   if (verifier) {
     verify_job =
@@ -652,15 +652,10 @@ ExtensionProtocolHandler::MaybeCreateJob(
       verify_job->Start(verifier);
   }
 
-  return new URLRequestExtensionJob(request,
-                                    network_delegate,
-                                    extension_id,
-                                    directory_path,
-                                    relative_path,
-                                    content_security_policy,
-                                    send_cors_header,
-                                    follow_symlinks_anywhere,
-                                    verify_job);
+  return new URLRequestExtensionJob(
+      request, network_delegate, extension_id, directory_path, relative_path,
+      content_security_policy, send_cors_header, follow_symlinks_anywhere,
+      std::move(verify_job));
 }
 
 bool ExtensionProtocolHandler::IsSafeRedirectTarget(
@@ -962,7 +957,7 @@ class ExtensionURLLoaderFactory : public network::mojom::URLLoaderFactory {
       scoped_refptr<ContentVerifier> content_verifier,
       const ExtensionResource& resource,
       scoped_refptr<net::HttpResponseHeaders> response_headers) {
-    ContentVerifyJob* verify_job = nullptr;
+    scoped_refptr<ContentVerifyJob> verify_job;
     if (content_verifier) {
       verify_job = content_verifier->CreateJobFor(resource.extension_id(),
                                                   resource.extension_root(),
@@ -973,7 +968,7 @@ class ExtensionURLLoaderFactory : public network::mojom::URLLoaderFactory {
 
     content::CreateFileURLLoader(
         request, std::move(loader), std::move(client),
-        std::make_unique<FileLoaderObserver>(verify_job),
+        std::make_unique<FileLoaderObserver>(std::move(verify_job)),
         std::move(response_headers));
   }