[Zucchini] Implement DisassemblerNoOp.

DisassemblerNoOp is a Disassembler that does not look for reference, and
used as fallback for patching Elements not recognised as executable.

Bug: 729154
Change-Id: I4cbf355fb59bcf7df12b9e6d81029c771c52f215
Reviewed-on: https://chromium-review.googlesource.com/599023Reviewed-by: Will Harris <wfh@chromium.org>
Commit-Queue: Etienne Pierre-Doray <etiennep@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491569}

chrome/installer/zucchini/BUILD.gn

@@ -17,6 +17,8 @@ static_library("zucchini_lib") {
     "crc32.h",
     "disassembler.cc",
     "disassembler.h",
+    "disassembler_no_op.cc",
+    "disassembler_no_op.h",
     "image_utils.h",
     "io_utils.cc",
     "io_utils.h",

chrome/installer/zucchini/disassembler_no_op.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 "chrome/installer/zucchini/disassembler_no_op.h"
+
+namespace zucchini {
+
+std::unique_ptr<DisassemblerNoOp> DisassemblerNoOp::Make(
+    ConstBufferView image) {
+  std::unique_ptr<DisassemblerNoOp> disasm(new DisassemblerNoOp());
+  if (!disasm->Parse(image))
+    return nullptr;
+  return disasm;
+}
+
+DisassemblerNoOp::DisassemblerNoOp() = default;
+DisassemblerNoOp::~DisassemblerNoOp() = default;
+
+ExecutableType DisassemblerNoOp::GetExeType() const {
+  return kExeTypeNoOp;
+}
+
+std::string DisassemblerNoOp::GetExeTypeString() const {
+  return "(Unknown)";
+}
+
+std::vector<ReferenceGroup> DisassemblerNoOp::GetReferenceGroups() const {
+  return std::vector<ReferenceGroup>();
+}
+
+bool DisassemblerNoOp::Parse(ConstBufferView image) {
+  return true;
+}
+
+}  // namespace zucchini

chrome/installer/zucchini/disassembler_no_op.h

+// 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.
+
+#ifndef CHROME_INSTALLER_ZUCCHINI_DISASSEMBLER_NO_OP_H_
+#define CHROME_INSTALLER_ZUCCHINI_DISASSEMBLER_NO_OP_H_
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "base/macros.h"
+#include "chrome/installer/zucchini/buffer_view.h"
+#include "chrome/installer/zucchini/disassembler.h"
+#include "chrome/installer/zucchini/image_utils.h"
+
+namespace zucchini {
+
+// This disassembler works on any file and does not look for reference.
+class DisassemblerNoOp : public Disassembler {
+ public:
+  static std::unique_ptr<DisassemblerNoOp> Make(ConstBufferView image);
+
+  ~DisassemblerNoOp() override;
+
+  // Disassembler:
+  ExecutableType GetExeType() const override;
+  std::string GetExeTypeString() const override;
+  std::vector<ReferenceGroup> GetReferenceGroups() const override;
+
+ protected:
+  DisassemblerNoOp();
+
+ private:
+  bool Parse(ConstBufferView image) override;
+
+  DISALLOW_COPY_AND_ASSIGN(DisassemblerNoOp);
+};
+
+}  // namespace zucchini
+
+#endif  // CHROME_INSTALLER_ZUCCHINI_DISASSEMBLER_NO_OP_H_