Implement SkPicture::bytesUsed() for SkRecord backend

tests/PictureTest.cpp

Index: tests/PictureTest.cpp
diff --git a/tests/PictureTest.cpp b/tests/PictureTest.cpp
index c87d9c75ca4048d8dac024028bb03c58845285f7..7fa6b9684ffee49ea0b56999eddee8250715eb24 100644
--- a/tests/PictureTest.cpp
+++ b/tests/PictureTest.cpp
@@ -1698,6 +1698,17 @@ static void test_gen_id(skiatest::Reporter* reporter) {
     REPORTER_ASSERT(reporter, hasData->uniqueID() != empty->uniqueID());
 }
 
+static void test_bytes_used(skiatest::Reporter* reporter) {
+    SkPictureRecorder recorder;
+
+    recorder.beginRecording(0, 0);
+    SkAutoTUnref<SkPicture> empty(recorder.endRecording());
+
+    // A SkPicture also has SkRecord and possibly SkBBHierarchy as members.
+    REPORTER_ASSERT(reporter, SkPictureUtils::approximateBytesUsed(empty.get()) >=
+                              sizeof(SkPicture));
+}
+
 DEF_TEST(Picture, reporter) {
 #ifdef SK_DEBUG
     test_deleting_empty_picture();
@@ -1723,6 +1734,7 @@ DEF_TEST(Picture, reporter) {
     test_clip_expansion(reporter);
     test_hierarchical(reporter);
     test_gen_id(reporter);
+    test_bytes_used(reporter);
 }
 
 #if SK_SUPPORT_GPU
@@ -1829,6 +1841,7 @@ struct CountingBBH : public SkBBoxHierarchy {
     virtual int getCount() const { return 0; }
     virtual int getDepth() const { return 0; }
     virtual void rewindInserts() {}
+    virtual size_t bytesUsed() const { return 0; }
 };
 
 class SpoonFedBBHFactory : public SkBBHFactory {