PDF: Return earlier when important tasks in Searchify fail

Skip further tasks whenever:
- The `perform_ocr_callback` passed to `Searchify` returns null.
- FPDFPage_GenerateContent() fails.

Bug: 331592549
Test: pdf_unittests --gtest_filter="PDFiumEngineExportsTest*"
Change-Id: If33bcc050c3527111b437541160b80ba97790567
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5491175
Commit-Queue: Chu-Hsuan Yang <chuhsuan@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1295238}

pdf/pdf.h

@@ -222,8 +222,6 @@ std::vector<uint8_t> ConvertPdfDocumentToNupPdf(
 #if BUILDFLAG(ENABLE_SCREEN_AI_SERVICE)
 // Converts an inaccessible PDF to a searchable PDF.
 // `pdf_buffer` is the buffer of the inaccessible PDF.
-// `searchified_callback` is the callback that is called with the searchified
-//     PDF when the conversion is done.
 // `perform_ocr_callback` is the callback that takes an image and outputs
 //     the OCR result. It may be called multiple times.
 //

pdf/pdfium/pdfium_engine_exports_unittest.cc

@@ -234,6 +234,25 @@ TEST_F(PDFiumEngineExportsTest, Searchify) {
                 testing::HasSubstr(kExpectedText));
   }
 }
+
+TEST_F(PDFiumEngineExportsTest, SearchifyBroken) {
+  base::FilePath pdf_path =
+      pdf_data_dir().Append(FILE_PATH_LITERAL("image_alt_text.pdf"));
+  std::optional<std::vector<uint8_t>> pdf_buffer =
+      base::ReadFileToBytes(pdf_path);
+  ASSERT_TRUE(pdf_buffer.has_value());
+
+  auto broken_perform_ocr_callback =
+      base::BindRepeating([](const SkBitmap& bitmap) {
+        auto annotation = screen_ai::mojom::VisualAnnotationPtr();
+        // Simulate the scenarios that fail to set the value of `annotation`.
+        CHECK(!annotation);
+        return annotation;
+      });
+  std::vector<uint8_t> output_pdf_buffer =
+      Searchify(*pdf_buffer, std::move(broken_perform_ocr_callback));
+  EXPECT_TRUE(output_pdf_buffer.empty());
+}
 #endif  // BUILDFLAG(ENABLE_SCREEN_AI_SERVICE)
 
 }  // namespace chrome_pdf

pdf/pdfium/pdfium_searchify.cc

@@ -238,14 +238,14 @@ std::vector<uint8_t> PDFiumSearchify(
       auto annotation = perform_ocr_callback.Run(bitmap);
       if (!annotation) {
         DLOG(ERROR) << "Failed to get OCR annotation on the image";
-        continue;
+        return {};
       }
       AddTextOnImage(document.get(), page.get(), font.get(), image,
                      std::move(annotation));
     }
     if (!FPDFPage_GenerateContent(page.get())) {
       DLOG(ERROR) << "Failed to generate content";
-      continue;
+      return {};
     }
   }
   PDFiumMemBufferFileWrite output_file_write;