Add a way to SuspendAll for a long duration

Hprof uses this mode to not cause thread suspend timeouts if GC tries
while the hprof dump is running.

Bug: 21063989
Change-Id: Ic6304620afd1489719a7e0e4299f829c90fe27cc
diff --git a/runtime/hprof/hprof.cc b/runtime/hprof/hprof.cc
index 88a72ec..917fe43 100644
--- a/runtime/hprof/hprof.cc
+++ b/runtime/hprof/hprof.cc
@@ -1214,7 +1214,7 @@
     // comment in Heap::VisitObjects().
     heap->IncrementDisableMovingGC(self);
   }
-  Runtime::Current()->GetThreadList()->SuspendAll(__FUNCTION__);
+  Runtime::Current()->GetThreadList()->SuspendAll(__FUNCTION__, true /* long suspend */);
   Hprof hprof(filename, fd, direct_to_ddms);
   hprof.Dump();
   Runtime::Current()->GetThreadList()->ResumeAll();