[tracing] Adding class-wise memory statistics to blink gc memory dumps

Source/platform/heap/ThreadState.h

Index: Source/platform/heap/ThreadState.h
diff --git a/Source/platform/heap/ThreadState.h b/Source/platform/heap/ThreadState.h
index 1f962b7df637954dde98307d775c2e98c3b961e5..2344ced678d4dec6feab755e2c3b26002c4f877d 100644
--- a/Source/platform/heap/ThreadState.h
+++ b/Source/platform/heap/ThreadState.h
@@ -490,8 +490,20 @@ public:
     void visitPersistents(Visitor*);
 
     struct GCSnapshotInfo {
+        // Map from gcInfoIndex to a snapshot class-ids (used as index below).

[haraken, 2015/06/27 07:27:40]

I'm wondering why you simply can't use gcInfoIndex as a tag. It is guaranteed
that gcInfoIndex returns an index in [0, # of classes actually used in this
execution).

+        using ClassTagMap = HashMap<size_t, size_t>;
+        ClassTagMap classTags;
+
+        // Map from class-id (index) to count/size.
+        Vector<int> liveCount;
+        Vector<int> deadCount;
+        Vector<size_t> liveSize;
+        Vector<size_t> deadSize;
+
         size_t currentHeapFreeSize;
         size_t currentHeapFreeCount;
+
+        size_t getClassTag(const size_t GCInfoIndex);
     };
 
 #if ENABLE(GC_PROFILING)
@@ -649,7 +661,8 @@ public:
 private:
     enum SnapshotType {
         HeapSnapshot,
-        FreelistSnapshot
+        FreelistSnapshot,
+        HeapSnapshotWithClasses
     };
 
     ThreadState();