Make valgrind happier and stop us leaking so much we can can't run the tests on a device.

Change-Id: Id8f45dde788fd84c10b0b5807b2d12eae529ba5e
diff --git a/src/runtime.h b/src/runtime.h
index 323c6c8..b6873e3 100644
--- a/src/runtime.h
+++ b/src/runtime.h
@@ -95,7 +95,8 @@
 
   Runtime() : stack_size_(0), thread_list_(NULL), class_linker_(NULL) {}
 
-  // Initializes a new uninitialized runtime.
+  void BlockSignals();
+
   bool Init(const Options& options, bool ignore_unrecognized);
 
   // The default stack size for managed threads created by the runtime.