Add error handling and unit test for pdf compositor service

components/printing/service/pdf_compositor_impl.cc

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/printing/service/pdf_compositor_impl.h"
 
 #include <utility>
 #include <vector>
 
 #include "base/logging.h"
@@ skipping 25 matching lines @@
 
   const MojoResult result = mojo::UnwrapSharedMemoryHandle(
       std::move(sk_handle), &memory_handle, &memory_size, &read_only_flag);
   DCHECK_EQ(MOJO_RESULT_OK, result);
   DCHECK_GT(memory_size, 0u);
 
   std::unique_ptr<base::SharedMemory> shm =
       base::MakeUnique<base::SharedMemory>(memory_handle, true);
   if (!shm->Map(memory_size)) {
     DLOG(ERROR) << "CompositePdf: Shared memory map failed.";
-    std::move(callback).Run(mojo::ScopedSharedBufferHandle());
+    std::move(callback).Run(mojom::PdfCompositor::Status::HANDLE_MAP_ERROR,
+                            mojo::ScopedSharedBufferHandle());
     return;
   }
 
   SkMemoryStream stream(shm->memory(), memory_size);
   int page_count = SkMultiPictureDocumentReadPageCount(&stream);
   if (!page_count) {
     DLOG(ERROR) << "CompositePdf: No page is read.";
-    std::move(callback).Run(mojo::ScopedSharedBufferHandle());
+    std::move(callback).Run(mojom::PdfCompositor::Status::CONTENT_FORMAT_ERROR,
+                            mojo::ScopedSharedBufferHandle());
     return;
   }
 
   std::vector<SkDocumentPage> pages(page_count);
   if (!SkMultiPictureDocumentRead(&stream, pages.data(), page_count)) {
     DLOG(ERROR) << "CompositePdf: Page reading failed.";
-    std::move(callback).Run(mojo::ScopedSharedBufferHandle());
+    std::move(callback).Run(mojom::PdfCompositor::Status::CONTENT_FORMAT_ERROR,
+                            mojo::ScopedSharedBufferHandle());
     return;
   }
 
   SkDynamicMemoryWStream wstream;
   sk_sp<SkDocument> doc = MakePdfDocument(creator_, &wstream);
 
   for (const auto& page : pages) {
     SkCanvas* canvas = doc->beginPage(page.fSize.width(), page.fSize.height());
     canvas->drawPicture(page.fPicture);
     doc->endPage();
   }
   doc->close();
 
   mojo::ScopedSharedBufferHandle buffer =
       mojo::SharedBufferHandle::Create(wstream.bytesWritten());
   DCHECK(buffer.is_valid());
 
   mojo::ScopedSharedBufferMapping mapping = buffer->Map(wstream.bytesWritten());
   DCHECK(mapping);
   wstream.copyToAndReset(mapping.get());
 
-  std::move(callback).Run(std::move(buffer));
+  std::move(callback).Run(mojom::PdfCompositor::Status::SUCCESS,
+                          std::move(buffer));
 }
 
 }  // namespace printing