Reduce header files including header files.

Main focus is getting heap.h out of runtime.h.

Change-Id: I8d13dce8512816db2820a27b24f5866cc871a04b
diff --git a/compiler/optimizing/pretty_printer.h b/compiler/optimizing/pretty_printer.h
index a7727c0..2c8166e 100644
--- a/compiler/optimizing/pretty_printer.h
+++ b/compiler/optimizing/pretty_printer.h
@@ -17,6 +17,7 @@
 #ifndef ART_COMPILER_OPTIMIZING_PRETTY_PRINTER_H_
 #define ART_COMPILER_OPTIMIZING_PRETTY_PRINTER_H_
 
+#include "base/stringprintf.h"
 #include "nodes.h"
 
 namespace art {