Reduce header files including header files.

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

Change-Id: I8d13dce8512816db2820a27b24f5866cc871a04b
diff --git a/runtime/gc/accounting/space_bitmap.cc b/runtime/gc/accounting/space_bitmap.cc
index 3cb8d94..436a5b5 100644
--- a/runtime/gc/accounting/space_bitmap.cc
+++ b/runtime/gc/accounting/space_bitmap.cc
@@ -72,6 +72,12 @@
 }
 
 template<size_t kAlignment>
+std::string SpaceBitmap<kAlignment>::Dump() const {
+  return StringPrintf("%s: %p-%p", name_.c_str(), reinterpret_cast<void*>(HeapBegin()),
+                      reinterpret_cast<void*>(HeapLimit()));
+}
+
+template<size_t kAlignment>
 void SpaceBitmap<kAlignment>::Clear() {
   if (bitmap_begin_ != NULL) {
     // This returns the memory to the system.  Successive page faults will return zeroed memory.