Avoid crash when reading from a temp file fails

Bug: 1153594
Change-Id: I7b3187024af0732f02d3f6dcd7f78cf1a1c510b0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2626198
Auto-Submit: Andrey Kosyakov <caseq@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#845110}

content/browser/devtools/devtools_stream_file.cc

@@ -110,16 +110,17 @@ void DevToolsStreamFile::ReadOnFileSequence(off_t position,
       } else {
         buffer.resize(size_got);
       }
-      data.reset(new std::string(std::move(buffer)));
       status = size_got ? StatusSuccess : StatusEOF;
       last_read_pos_ = position + size_got;
+      if (binary_) {
+        data = std::make_unique<std::string>();
+        base::Base64Encode(buffer, data.get());
+        base64_encoded = true;
+      } else {
+        data = std::make_unique<std::string>(std::move(buffer));
+      }
     }
   }
-  if (binary_) {
-    std::string raw_data(std::move(*data));
-    base::Base64Encode(raw_data, data.get());
-    base64_encoded = true;
-  }
   GetUIThreadTaskRunner({})->PostTask(
       FROM_HERE, base::BindOnce(std::move(callback), std::move(data),
                                 base64_encoded, status));