Factor out edge marking logic from Plan::AddSubTarget

Move the logic to mark edges as wanted over to a Plan::EdgeWanted method
so it can be re-used elsewhere later.

src/build.cc

@@ -327,11 +327,9 @@ bool Plan::AddSubTarget(Node* node, Node* dependent, string* err) {
   // mark it now.
   if (node->dirty() && want == kWantNothing) {
     want = kWantToStart;
-    ++wanted_edges_;
+    EdgeWanted(edge);
     if (edge->AllInputsReady())
       ScheduleWork(want_ins.first);
-    if (!edge->is_phony())
-      ++command_edges_;
   }
 
   if (!want_ins.second)
@@ -346,6 +344,12 @@ bool Plan::AddSubTarget(Node* node, Node* dependent, string* err) {
   return true;
 }
 
+void Plan::EdgeWanted(Edge* edge) {
+  ++wanted_edges_;
+  if (!edge->is_phony())
+    ++command_edges_;
+}
+
 Edge* Plan::FindWork() {
   if (ready_.empty())
     return NULL;

src/build.h

@@ -96,6 +96,8 @@ private:
     kWantToFinish
   };
 
+  void EdgeWanted(Edge* edge);
+
   /// Submits a ready edge as a candidate for execution.
   /// The edge may be delayed from running, for example if it's a member of a
   /// currently-full pool.