Update the digest when encountering DrawTextBlobOps.

Text operations are tracked via the 2D canvas context digest, not the
PaintOp digest. Because these digests are maintained separately, without
this change, drawing a rectangle and then text wouldn't be distinguised
from drawing text than then a rectangle in the final, combined digest.

Bug: 973801
Change-Id: If237733320d0a2e3ce95dcbd3bc2f97c69d888bb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2327132
Commit-Queue: Caleb Raitto <caraitto@chromium.org>
Reviewed-by: Khushal <khushalsagar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#795729}

third_party/blink/renderer/platform/graphics/identifiability_paint_op_digest.cc

@@ -90,9 +90,15 @@ void IdentifiabilityPaintOpDigest::MaybeUpdateDigest(
       break;
 
     // To capture font fallback identifiability, we capture text draw operations
-    // at the 2D context layer.
-    if (op->GetType() == cc::PaintOpType::DrawTextBlob)
+    // at the 2D context layer. We still need to modify the token builder digest
+    // since we want to track the relative ordering of text operations and other
+    // operations.
+    if (op->GetType() == cc::PaintOpType::DrawTextBlob) {
+      constexpr uint64_t kDrawTextBlobValue =
+          UINT64_C(0x8c1587a34065ea3b);  // Picked form a hat.
+      builder_.AddValue(kDrawTextBlobValue);
       continue;
+    }
 
     // DrawRecord PaintOps contain nested PaintOps.
     if (op->GetType() == cc::PaintOpType::DrawRecord) {

third_party/blink/renderer/platform/graphics/identifiability_paint_op_digest_unittest.cc

@@ -103,21 +103,64 @@ TEST(IdentifiabilityPaintOpDigestTest, DigestIsInitialIfNotInStudy) {
       identifiability_paintop_digest.encountered_partially_digested_image());
 }
 
-TEST(IdentifiabilityPaintOpDigestTest, SkipsTextOps) {
+TEST(IdentifiabilityPaintOpDigestTest, IgnoresTextOpsContents) {
   StudyParticipationRaii study_participation_raii;
-  IdentifiabilityPaintOpDigest identifiability_paintop_digest(kSize);
-  auto paint_record = sk_make_sp<cc::PaintRecord>();
-  paint_record->push<cc::DrawTextBlobOp>(
+  IdentifiabilityPaintOpDigest identifiability_paintop_digest1(kSize);
+  IdentifiabilityPaintOpDigest identifiability_paintop_digest2(kSize);
+  auto paint_record1 = sk_make_sp<cc::PaintRecord>();
+  auto paint_record2 = sk_make_sp<cc::PaintRecord>();
+  paint_record1->push<cc::DrawTextBlobOp>(
       SkTextBlob::MakeFromString("abc", SkFont(SkTypeface::MakeDefault())),
       1.0f, 1.0f, cc::PaintFlags());
-  identifiability_paintop_digest.MaybeUpdateDigest(paint_record,
-                                                   /*num_ops_to_visit=*/1);
-  EXPECT_EQ(kTokenBuilderInitialDigest,
-            identifiability_paintop_digest.GetToken().ToUkmMetricValue());
+  paint_record2->push<cc::DrawTextBlobOp>(
+      SkTextBlob::MakeFromString("def", SkFont(SkTypeface::MakeDefault())),
+      2.0f, 2.0f, cc::PaintFlags());
+  identifiability_paintop_digest1.MaybeUpdateDigest(paint_record1,
+                                                    /*num_ops_to_visit=*/1);
+  identifiability_paintop_digest2.MaybeUpdateDigest(paint_record2,
+                                                    /*num_ops_to_visit=*/1);
+  EXPECT_EQ(identifiability_paintop_digest1.GetToken().ToUkmMetricValue(),
+            identifiability_paintop_digest2.GetToken().ToUkmMetricValue());
+  EXPECT_NE(kTokenBuilderInitialDigest,
+            identifiability_paintop_digest1.GetToken().ToUkmMetricValue());
+  EXPECT_EQ(INT64_C(5364951310489041526),
+            identifiability_paintop_digest1.GetToken().ToUkmMetricValue());
 
-  EXPECT_FALSE(identifiability_paintop_digest.encountered_skipped_ops());
+  EXPECT_FALSE(identifiability_paintop_digest1.encountered_skipped_ops());
   EXPECT_FALSE(
-      identifiability_paintop_digest.encountered_partially_digested_image());
+      identifiability_paintop_digest1.encountered_partially_digested_image());
+  EXPECT_FALSE(identifiability_paintop_digest2.encountered_skipped_ops());
+  EXPECT_FALSE(
+      identifiability_paintop_digest2.encountered_partially_digested_image());
+}
+
+TEST(IdentifiabilityPaintOpDigestTest, RelativeOrderingTextOpsAndOtherOps) {
+  StudyParticipationRaii study_participation_raii;
+  IdentifiabilityPaintOpDigest identifiability_paintop_digest1(kSize);
+  IdentifiabilityPaintOpDigest identifiability_paintop_digest2(kSize);
+  auto paint_record1 = sk_make_sp<cc::PaintRecord>();
+  auto paint_record2 = sk_make_sp<cc::PaintRecord>();
+  paint_record1->push<cc::DrawTextBlobOp>(
+      SkTextBlob::MakeFromString("abc", SkFont(SkTypeface::MakeDefault())),
+      1.0f, 1.0f, cc::PaintFlags());
+  paint_record1->push<cc::ScaleOp>(kScaleX, kScaleY);
+  paint_record2->push<cc::ScaleOp>(kScaleX, kScaleY);
+  paint_record2->push<cc::DrawTextBlobOp>(
+      SkTextBlob::MakeFromString("abc", SkFont(SkTypeface::MakeDefault())),
+      1.0f, 1.0f, cc::PaintFlags());
+  identifiability_paintop_digest1.MaybeUpdateDigest(paint_record1,
+                                                    /*num_ops_to_visit=*/1);
+  identifiability_paintop_digest2.MaybeUpdateDigest(paint_record2,
+                                                    /*num_ops_to_visit=*/1);
+  EXPECT_NE(identifiability_paintop_digest1.GetToken().ToUkmMetricValue(),
+            identifiability_paintop_digest2.GetToken().ToUkmMetricValue());
+
+  EXPECT_FALSE(identifiability_paintop_digest1.encountered_skipped_ops());
+  EXPECT_FALSE(
+      identifiability_paintop_digest1.encountered_partially_digested_image());
+  EXPECT_FALSE(identifiability_paintop_digest2.encountered_skipped_ops());
+  EXPECT_FALSE(
+      identifiability_paintop_digest2.encountered_partially_digested_image());
 }
 
 TEST(IdentifiabilityPaintOpDigestTest, SkPathDigestStability) {