Precache manifest should not be added to fetcher pool which is full

components/precache/core/precache_fetcher.cc

Index: components/precache/core/precache_fetcher.cc
diff --git a/components/precache/core/precache_fetcher.cc b/components/precache/core/precache_fetcher.cc
index eb9aeba0a15504b0b22cd635a144f74766f478f2..875e3e9515ad38f6037d3d7088e6443717ae2362 100644
--- a/components/precache/core/precache_fetcher.cc
+++ b/components/precache/core/precache_fetcher.cc
@@ -399,14 +399,11 @@ void PrecacheFetcher::StartNextResourceFetch() {
 }
 
 void PrecacheFetcher::StartNextManifestFetch() {
-  if (manifest_urls_to_fetch_.empty())
+  if (manifest_urls_to_fetch_.empty() || !pool_.IsAvailable())

[bengr, 2016/06/06 18:55:15]

Could you add a test that tries to precache more resources and manifests than
could fit at once in the pool?

[Raj, 2016/06/08 03:10:42]

Done.

     return;
 
   // We only fetch one manifest at a time to keep the size of
   // resource_urls_to_fetch_ as small as possible.
-  DCHECK(pool_.IsAvailable())
-      << "There are no available parallel requests to fetch the next manifest. "
-         "Did you forget to call Delete?";
   VLOG(3) << "Fetching " << manifest_urls_to_fetch_.front();
   pool_.Add(base::WrapUnique(new Fetcher(
       request_context_.get(), manifest_urls_to_fetch_.front(),