Refactoring: HashMap: provide a pointer match function, so users don't need to.

src/heap-snapshot-generator.cc

Index: src/heap-snapshot-generator.cc
diff --git a/src/heap-snapshot-generator.cc b/src/heap-snapshot-generator.cc
index 0f3e6ad413f270719dc546e792aa45ce8ebf73bc..545e990e1a1d35d723045d1851ed52fabcc7b26a 100644
--- a/src/heap-snapshot-generator.cc
+++ b/src/heap-snapshot-generator.cc
@@ -732,7 +732,7 @@ size_t HeapObjectsMap::GetUsedMemorySize() const {
 
 
 HeapEntriesMap::HeapEntriesMap()
-    : entries_(HeapThingsMatch) {
+    : entries_(HashMap::PointersMatch) {
 }
 
 
@@ -751,7 +751,7 @@ void HeapEntriesMap::Pair(HeapThing thing, int entry) {
 
 
 HeapObjectsSet::HeapObjectsSet()
-    : entries_(HeapEntriesMap::HeapThingsMatch) {
+    : entries_(HashMap::PointersMatch) {
 }