Wire up hprof.

I tested this with test 074-gc-thrash, which creates a .hprof file
that can be read with hat.

Change-Id: Ie75b7a7cf3c2ee32189df47ab0129e99449ebc6c
diff --git a/src/object.h b/src/object.h
index 6610871..dd2c1ca 100644
--- a/src/object.h
+++ b/src/object.h
@@ -1504,10 +1504,10 @@
   }
 
   size_t GetObjectSize() const {
-    CHECK(!IsVariableSize());
+    CHECK(!IsVariableSize()) << " class=" << PrettyTypeOf(this);
     DCHECK_EQ(sizeof(size_t), sizeof(int32_t));
     size_t result = GetField32(OFFSET_OF_OBJECT_MEMBER(Class, object_size_), false);
-    CHECK_GE(result, sizeof(Object));
+    CHECK_GE(result, sizeof(Object)) << " class=" << PrettyTypeOf(this);
     return result;
   }