Fix initializer lists to be Google C++ style.

Change-Id: Iada52ea5cf95492684033993b3299042bdaf6cee
diff --git a/src/stack.cc b/src/stack.cc
index 07a1cb1..e7c632c 100644
--- a/src/stack.cc
+++ b/src/stack.cc
@@ -173,8 +173,8 @@
 size_t StackVisitor::ComputeNumFrames() const {
   struct NumFramesVisitor : public StackVisitor {
     explicit NumFramesVisitor(const ManagedStack* stack,
-                              const std::vector<TraceStackFrame>* trace_stack) :
-                                StackVisitor(stack, trace_stack), frames(0) {}
+                              const std::vector<TraceStackFrame>* trace_stack)
+        : StackVisitor(stack, trace_stack), frames(0) {}
 
     virtual bool VisitFrame() {
       frames++;