8011343: Add new flag for verifying the heap during startup

Perform verification during VM startup under control of new flag and within a VMOperation.

Reviewed-by: stefank, jmasa, brutisso

hotspot/src/share/vm/memory/genCollectedHeap.cpp

@@ -819,12 +819,13 @@ bool GenCollectedHeap::is_in_young(oop p) {
 // Returns "TRUE" iff "p" points into the committed areas of the heap.
 bool GenCollectedHeap::is_in(const void* p) const {
   #ifndef ASSERT
-  guarantee(VerifyBeforeGC   ||
-            VerifyDuringGC   ||
-            VerifyBeforeExit ||
-            PrintAssembly    ||
-            tty->count() != 0 ||   // already printing
-            VerifyAfterGC    ||
+  guarantee(VerifyBeforeGC      ||
+            VerifyDuringGC      ||
+            VerifyBeforeExit    ||
+            VerifyDuringStartup ||
+            PrintAssembly       ||
+            tty->count() != 0   ||   // already printing
+            VerifyAfterGC       ||
     VMError::fatal_error_in_progress(), "too expensive");
 
   #endif