Increased default size of thread stack.

Browser JavaScript was overflowing the stack previously.

Change-Id: I922a3ac9a1d2fefe1a201118a2c8129f3fd3eae8
diff --git a/src/thread.h b/src/thread.h
index 37425ff..a100c03 100644
--- a/src/thread.h
+++ b/src/thread.h
@@ -92,7 +92,7 @@
   static const size_t kStackOverflowReservedBytes = 8 * KB;
 #endif
 
-  static const size_t kDefaultStackSize = 96 * KB;
+  static const size_t kDefaultStackSize = 128 * KB;
 
   class StackVisitor {
    public: