Make FPDFAnnotEmbedderTest.Bug1206 resiliant to changes

Instead of hard coding the expected output size, use the initial output
size as the basis for comparison.

Bug: pdfium:1206
Change-Id: I8f2b6dba7721c24d0d5d6eb248be6d846877b1d4
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/117452
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Thomas Sepez <tsepez@google.com>
diff --git a/fpdfsdk/fpdf_annot_embeddertest.cpp b/fpdfsdk/fpdf_annot_embeddertest.cpp
index 2983a7d..a9d83df 100644
--- a/fpdfsdk/fpdf_annot_embeddertest.cpp
+++ b/fpdfsdk/fpdf_annot_embeddertest.cpp
@@ -2203,7 +2203,7 @@
     }
     return "0d9fc05c6762fd788bd23fd87a4967bc";
   }();
-  static constexpr size_t kExpectedSize = 1601;
+  static constexpr size_t kExpectedMinimumOriginalSize = 1601;
 
   ASSERT_TRUE(OpenDocument("bug_1206.pdf"));
 
@@ -2211,7 +2211,8 @@
   ASSERT_TRUE(page);
 
   ASSERT_TRUE(FPDF_SaveAsCopy(document(), this, 0));
-  EXPECT_EQ(kExpectedSize, GetString().size());
+  const size_t original_size = GetString().size();
+  EXPECT_LE(kExpectedMinimumOriginalSize, original_size);  // Sanity check.
   ClearString();
 
   for (size_t i = 0; i < 10; ++i) {
@@ -2221,7 +2222,7 @@
     ASSERT_TRUE(FPDF_SaveAsCopy(document(), this, 0));
     // TODO(https://crbug.com/pdfium/1206): This is wrong. The size should be
     // equal, not bigger.
-    EXPECT_LT(kExpectedSize, GetString().size());
+    EXPECT_GT(GetString().size(), original_size);
     ClearString();
   }