Implement SkPicture::bytesUsed() for SkRecord backend

src/core/SkRecord.h

Index: src/core/SkRecord.h
diff --git a/src/core/SkRecord.h b/src/core/SkRecord.h
index 6019e0340683c9f2077b04c3868ace677c0e2687..521fd38014fc889a7a71469f596e9ee38004961c 100644
--- a/src/core/SkRecord.h
+++ b/src/core/SkRecord.h
@@ -30,7 +30,7 @@ class SkRecord : SkNoncopyable {
         kFirstReserveCount = 64 / sizeof(void*),
     };
 public:
-    SkRecord() : fCount(0), fReserved(0) {}
+    SkRecord() : fCount(0), fReserved(0), fBytesAllocated(0) {}
 
     ~SkRecord() {
         Destroyer destroyer;
@@ -68,6 +68,7 @@ public:
     template <typename T>
     T* alloc(size_t count = 1) {
         // Bump up to the next pointer width if needed, so all allocations start pointer-aligned.
+        fBytesAllocated += sizeof(T) * count;
         return (T*)fAlloc.alloc(sizeof(T) * count, SK_MALLOC_THROW);
     }
 
@@ -113,6 +114,10 @@ public:
         return fRecords[i].set(this->allocCommand<T>());
     }
 
+    size_t bytesUsed() const { return fBytesAllocated +
+                                      fReserved * (sizeof(Record) + sizeof(Type8)) +
+                                      sizeof(SkRecord); }
+
 private:
     // Implementation notes!
     //
@@ -231,6 +236,9 @@ private:
     // fCount and fReserved measure both fRecords and fTypes, which always grow in lock step.
     unsigned fCount;
     unsigned fReserved;
+
+    // counts bytes we've requested in fAlloc; *not* bytes in fRecords or fTypes
+    unsigned fBytesAllocated;
 };
 
 #endif//SkRecord_DEFINED