Backgroundtracing: Fixed preemptive reports

BackgroundTracingManagerImpl::GenerateMetadataDict was checking
IsAllowedFinalization() which blocks every preemptive report
from getting this metadata added, as it sets a 7-week cooldown
on new reports just prior to this.

R=etienneb@chromium.org

Change-Id: I3bc44958a304397e4eb6a2db66432ec45454d6f0
Reviewed-on: https://chromium-review.googlesource.com/1148776Reviewed-by: Erik Chen <erikchen@chromium.org>
Commit-Queue: oysteine <oysteine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577676}

content/browser/tracing/background_tracing_manager_impl.cc

@@ -561,9 +561,6 @@ bool BackgroundTracingManagerImpl::IsAllowedFinalization() const {
 
 std::unique_ptr<base::DictionaryValue>
 BackgroundTracingManagerImpl::GenerateMetadataDict() {
-  if (!IsAllowedFinalization())
-    return nullptr;
-
   auto metadata_dict = std::make_unique<base::DictionaryValue>();
   if (config_) {
     auto config_dict = std::make_unique<base::DictionaryValue>();