Fuzzer for FileSystemManagerImpl mojo interface.

This is a rebase of adetaylor@'s original CL
https://chromium-review.googlesource.com/c/chromium/src/+/2253149
on top of the refactorings.

Bug: 1105910
Change-Id: Ic6dc70400bcb9aec9f37981ed5e41fa5eb6fa3bb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2410491
Commit-Queue: Mark Brand <markbrand@google.com>
Reviewed-by: Jonathan Metzman <metzman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#811682}

content/test/fuzzer/BUILD.gn

@@ -187,6 +187,24 @@ mojolpm_fuzzer_test("code_cache_host_mojolpm_fuzzer") {
   ]
 }
 
+mojolpm_fuzzer_test("file_system_manager_mojolpm_fuzzer") {
+  sources = [ "file_system_manager_mojolpm_fuzzer.cc" ]
+
+  proto_source = "file_system_manager_mojolpm_fuzzer.proto"
+
+  deps = [
+    "//base/test:test_support",
+    "//content/browser:for_content_tests",
+    "//content/public/browser:browser_sources",
+    "//content/test:test_support",
+    "//services/network:test_support",
+    "//storage/browser:test_support",
+    "//third_party/icu:icudata",
+  ]
+
+  proto_deps = [ "//third_party/blink/public/mojom:mojom_platform_mojolpm" ]
+}
+
 fuzzer_test("speech_audio_encoder_fuzzer") {
   sources = [
     "../../browser/speech/audio_buffer.cc",

content/test/fuzzer/file_system_manager_mojolpm_fuzzer.proto

+// Copyright 2020 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.
+
+// Message format for the MojoLPM fuzzer for the FileSystemManager interface.
+
+syntax = "proto2";
+
+package content.fuzzing.file_system_manager.proto;
+
+import "third_party/blink/public/mojom/filesystem/file_system.mojom.mojolpm.proto";
+
+// Bind a new FileSystemManager remote
+message NewFileSystemManagerAction {
+  enum RenderProcessId {
+    ZERO = 0;
+    ONE = 1;
+  }
+
+  required uint32 id = 1;
+  required RenderProcessId render_process_id = 2;
+}
+
+// Run the specific sequence for (an indeterminate) period. This is not
+// intended to create a specific ordering, but to allow the fuzzer to delay a
+// later task until previous tasks have completed.
+message RunThreadAction {
+  enum ThreadId {
+    IO = 0;
+    UI = 1;
+  }
+
+  required ThreadId id = 1;
+}
+
+// Actions that can be performed by the fuzzer.
+message Action {
+  oneof action {
+    NewFileSystemManagerAction new_file_system_manager = 1;
+    RunThreadAction run_thread = 2;
+    mojolpm.blink.mojom.FileSystemManager.RemoteAction
+        file_system_manager_remote_action = 3;
+    mojolpm.blink.mojom.FileSystemCancellableOperation.RemoteAction
+        file_system_cancellable_operation_remote_action = 4;
+  }
+}
+
+// Sequence provides a level of indirection which allows Testcase to compactly
+// express repeated sequences of actions.
+message Sequence {
+  repeated uint32 action_indexes = 1 [packed = true];
+}
+
+// Testcase is the top-level message type interpreted by the fuzzer.
+message Testcase {
+  repeated Action actions = 1;
+  repeated Sequence sequences = 2;
+  repeated uint32 sequence_indexes = 3 [packed = true];
+}
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