Factor IOTaskRunnerTestingPlatformSupport out for reusing it

This CL factor IOTaskRunnerTestingPlatformSupport out of
modules/mediastream/media_stream_video_capturer_source_test.cc
into a helper class/file
platform/testing/io_task_runner_testing_platform_support.cc|h.

This allows it to be reusable.

This is a preparation CL for crrev.com/c/1600898.

R=haraken@chromium.org,guidou@chromium.org

BUG=787261

Change-Id: I2d5a11d4a93c19b27dc4290d025be10a9502c890
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1602593Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Guido Urdaneta <guidou@chromium.org>
Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Commit-Queue: Antonio Gomes <tonikitoo@igalia.com>
Cr-Commit-Position: refs/heads/master@{#658370}

third_party/blink/renderer/modules/mediastream/media_stream_video_capturer_source_test.cc

@@ -21,7 +21,7 @@
 #include "third_party/blink/renderer/platform/cross_thread_functional.h"
 #include "third_party/blink/renderer/platform/scheduler/public/post_cross_thread_task.h"
 #include "third_party/blink/renderer/platform/scheduler/public/thread.h"
-#include "third_party/blink/renderer/platform/testing/testing_platform_support.h"
+#include "third_party/blink/renderer/platform/testing/io_task_runner_testing_platform_support.h"
 #include "third_party/blink/renderer/platform/wtf/functional.h"
 
 using ::testing::_;
@@ -31,19 +31,6 @@ namespace blink {
 
 namespace {
 
-class IOTaskRunnerTestingPlatformSupport : public TestingPlatformSupport {
- public:
-  IOTaskRunnerTestingPlatformSupport()
-      : io_thread_(Thread::CreateThread(
-            ThreadCreationParams(WebThreadType::kTestThread))) {}
-  scoped_refptr<base::SingleThreadTaskRunner> GetIOTaskRunner() const override {
-    return io_thread_->GetTaskRunner();
-  }
-
- private:
-  std::unique_ptr<Thread> io_thread_;
-};
-
 class MockVideoCapturerSource : public media::VideoCapturerSource {
  public:
   MockVideoCapturerSource() {}

third_party/blink/renderer/platform/BUILD.gn

@@ -1581,6 +1581,8 @@ jumbo_static_library("test_support") {
     "testing/fuzzed_data_provider.h",
     "testing/histogram_tester.cc",
     "testing/histogram_tester.h",
+    "testing/io_task_runner_testing_platform_support.cc",
+    "testing/io_task_runner_testing_platform_support.h",
     "testing/layer_tree_host_embedder.cc",
     "testing/layer_tree_host_embedder.h",
     "testing/message_loop_for_mojo.h",

third_party/blink/renderer/platform/testing/io_task_runner_testing_platform_support.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 "third_party/blink/renderer/platform/testing/io_task_runner_testing_platform_support.h"
+
+#include "base/single_thread_task_runner.h"
+#include "third_party/blink/renderer/platform/scheduler/public/thread.h"
+
+namespace blink {
+
+IOTaskRunnerTestingPlatformSupport::IOTaskRunnerTestingPlatformSupport()
+    : io_thread_(Thread::CreateThread(
+          ThreadCreationParams(WebThreadType::kTestThread))) {}
+
+scoped_refptr<base::SingleThreadTaskRunner>
+IOTaskRunnerTestingPlatformSupport::GetIOTaskRunner() const {
+  return io_thread_->GetTaskRunner();
+}
+
+}  // namespace blink

third_party/blink/renderer/platform/testing/io_task_runner_testing_platform_support.h

+// 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.
+
+#ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_TESTING_IO_TASK_RUNNER_TESTING_PLATFORM_SUPPORT_H_
+#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_TESTING_IO_TASK_RUNNER_TESTING_PLATFORM_SUPPORT_H_
+
+#include "third_party/blink/renderer/platform/testing/testing_platform_support.h"
+
+#include "base/memory/scoped_refptr.h"
+
+namespace base {
+class SingleThreadTaskRunner;
+}
+
+namespace blink {
+
+class Thread;
+
+class IOTaskRunnerTestingPlatformSupport : public TestingPlatformSupport {
+ public:
+  IOTaskRunnerTestingPlatformSupport();
+
+  scoped_refptr<base::SingleThreadTaskRunner> GetIOTaskRunner() const override;
+
+ private:
+  std::unique_ptr<Thread> io_thread_;
+};
+
+}  // namespace blink
+
+#endif  // THIRD_PARTY_BLINK_RENDERER_PLATFORM_TESTING_IO_TASK_RUNNER_TESTING_PLATFORM_SUPPORT_H_