Create the BackgroundFetchBatchManager and initiate a download.

content/browser/background_fetch/background_fetch_context.cc

Index: content/browser/background_fetch/background_fetch_context.cc
diff --git a/content/browser/background_fetch/background_fetch_context.cc b/content/browser/background_fetch/background_fetch_context.cc
index 5e7301c48c1f952245b83300bd1c980d4d0e27b9..dd87ffd075c9d1737960653609b3ce30da6a8ed5 100644
--- a/content/browser/background_fetch/background_fetch_context.cc
+++ b/content/browser/background_fetch/background_fetch_context.cc
@@ -4,6 +4,7 @@
 
 #include "content/browser/background_fetch/background_fetch_context.h"
 
+#include "content/browser/background_fetch/batch_request.h"
 #include "content/browser/background_fetch/fetch_request.h"
 #include "content/browser/service_worker/service_worker_context_wrapper.h"
 #include "content/public/browser/browser_context.h"
@@ -15,8 +16,10 @@ namespace content {
 
 BackgroundFetchContext::BackgroundFetchContext(
     BrowserContext* browser_context,
+    StoragePartition* storage_partition,
     const scoped_refptr<ServiceWorkerContextWrapper>& service_worker_context)
     : service_worker_context_(service_worker_context),
+      background_fetch_batch_manager_(browser_context, storage_partition),
       background_fetch_data_manager_(this) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   // TODO(harkness): BackgroundFetchContext should have
@@ -32,19 +35,24 @@ void BackgroundFetchContext::Init() {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
   // TODO(harkness): Create the Download observer.
-  // TODO(harkness): Create the Batch manager.
 }
 
 void BackgroundFetchContext::Shutdown() {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 }
 
-void BackgroundFetchContext::CreateRequest(const FetchRequest& fetch_request) {
+void BackgroundFetchContext::CreateRequest(
+    const BatchRequest& batch_request,
+    const std::vector<FetchRequest>& fetch_requests) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  DCHECK(fetch_requests.size());

[Peter Beverloo, 2017/02/23 12:14:59]

DCHECK_GE, since you're interested in the count, not whether it evaluates to
TRUE (despite that having the same effect in this case).

The difference is in the error reporting you get. With DCHECK, you'd get
something like "fetch_requests.size() evaluates to false". With DCHECK_GE you'd
get something like "expected fetch_requests.size() to be greater or equal to X,
was Y". That'll make crash reports down the line WAY more useful.

[harkness, 2017/02/23 17:08:41]

Done.

   // Inform the data manager about the new download.
-  background_fetch_data_manager_.CreateRequest(fetch_request);
+  // TODO(harkness): Create the batch metadata in the data_manager and return a
+  // callback that can be given to the BatchManager.
+  background_fetch_data_manager_.CreateRequest(fetch_requests[0]);
 
-  // TODO(harkness): Make the request to the download manager.
+  background_fetch_batch_manager_.ProcessBatch(batch_request.guid(),
+                                               fetch_requests);
 }
 
 }  // namespace content