[BlobAsync] Faster shortcuttin, make renderer controller leaky & alive.

storage/browser/blob/blob_async_builder_host.cc

Index: storage/browser/blob/blob_async_builder_host.cc
diff --git a/storage/browser/blob/blob_async_builder_host.cc b/storage/browser/blob/blob_async_builder_host.cc
index 3091604804d33d963604d3ca5282bee112325885..ffa713e68e1e26ee82dd8fffaa23bcd21daed532 100644
--- a/storage/browser/blob/blob_async_builder_host.cc
+++ b/storage/browser/blob/blob_async_builder_host.cc
@@ -96,9 +96,6 @@ BlobTransportResult BlobAsyncBuilderHost::StartBuildingBlob(
     BlobStorageContext* context,
     const RequestMemoryCallback& request_memory) {
   DCHECK(context);
-  if (async_blob_map_.find(uuid) == async_blob_map_.end()) {
-    return BlobTransportResult::BAD_IPC;
-  }
 
   // Step 1: Get the sizes.
   size_t shortcut_memory_size_bytes = 0;
@@ -271,9 +268,7 @@ void BlobAsyncBuilderHost::CancelBuildingBlob(const std::string& uuid,
                                               BlobStorageContext* context) {
   DCHECK(context);
   auto state_it = async_blob_map_.find(uuid);
-  if (state_it == async_blob_map_.end()) {
-    return;
-  }
+  DCHECK(state_it != async_blob_map_.end());
   // We can have the blob dereferenced by the renderer, but have it still being
   // 'built'. In this case, it's destructed in the context, but we still have
   // it in our map. Hence we make sure the context has the entry before