[omnibox] Minor fuzzer for AutocompleteInput

Adds a small fuzzer for AutocompleteInput, an input classifier
and state structure.

Change-Id: Ib73721b44a9ef6ca15e978fcea210e56fd40be30
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1862346
Commit-Queue: Kevin Bailey <krb@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Justin Donnelly <jdonnelly@chromium.org>
Reviewed-by: Max Moroz <mmoroz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#706619}

components/omnibox/browser/BUILD.gn

@@ -7,6 +7,7 @@ import("//build/config/jumbo.gni")
 import("//build/config/ui.gni")
 import("//components/vector_icons/vector_icons.gni")
 import("//device/vr/buildflags/buildflags.gni")
+import("//testing/libfuzzer/fuzzer_test.gni")
 import("//third_party/protobuf/proto_library.gni")
 
 if (is_android) {
@@ -453,3 +454,16 @@ source_set("unit_tests") {
     "//url",
   ]
 }
+
+fuzzer_test("autocomplete_input_fuzzer") {
+  sources = [
+    "autocomplete_input_fuzzer.cc",
+  ]
+  deps = [
+    ":browser",
+    ":test_support",
+    "//base",
+    "//base:i18n",
+    "//third_party/metrics_proto:metrics_proto",
+  ]
+}

components/omnibox/browser/autocomplete_input_fuzzer.cc

+// Copyright 2019 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/omnibox/browser/autocomplete_input.h"
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "base/at_exit.h"
+#include "base/i18n/icu_util.h"
+#include "base/strings/string16.h"
+#include "components/omnibox/browser/test_scheme_classifier.h"
+#include "third_party/metrics_proto/omnibox_event.pb.h"
+
+// From crbug.com/774858
+struct IcuEnvironment {
+  IcuEnvironment() { CHECK(base::i18n::InitializeICU()); }
+  // Used by ICU integration.
+  base::AtExitManager at_exit_manager;
+};
+
+IcuEnvironment icu_env;
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
+  // This fuzzer creates a random UTF16 string, for testing primarily against
+  // AutocompleteInput::Parse().
+  base::string16 s(reinterpret_cast<const base::string16::value_type*>(data),
+                   size / sizeof(base::string16::value_type));
+  AutocompleteInput input(s, metrics::OmniboxEventProto::OTHER,
+                          TestSchemeClassifier());
+  return 0;
+}