Don't try to access an Isolate when don't have one yet.

BUG=373385
R=jochen@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/289033006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@270986 0039d316-1c4b-4281-b951-d872f2087c98

content/child/content_child_helpers.cc

@@ -29,7 +29,9 @@ size_t GetMemoryUsageKB() {
   v8::HeapStatistics stat;
   // TODO(svenpanne) The call below doesn't take web workers into account, this
   // has to be done manually by iterating over all Isolates involved.
-  v8::Isolate::GetCurrent()->GetHeapStatistics(&stat);
+  v8::Isolate* isolate = v8::Isolate::GetCurrent();
+  if (isolate)
+    isolate->GetHeapStatistics(&stat);
   return mem_usage + (static_cast<uint64_t>(stat.total_heap_size()) >> 10);
 }
 #elif defined(OS_MACOSX)