mv FetchTestingPlatformSupport to platform/loader/testing

third_party/WebKit/Source/platform/BUILD.gn

Index: third_party/WebKit/Source/platform/BUILD.gn
diff --git a/third_party/WebKit/Source/platform/BUILD.gn b/third_party/WebKit/Source/platform/BUILD.gn
index 0a638a30bd05b4d0d6cc227a046dff72bbd50d65..d50fa0f165fae9cc2e188990a28ae2b6f815a807 100644
--- a/third_party/WebKit/Source/platform/BUILD.gn
+++ b/third_party/WebKit/Source/platform/BUILD.gn
@@ -1559,6 +1559,9 @@ static_library("test_support") {
     "loader/fetch/MockResource.h",
     "loader/fetch/MockResourceClient.cpp",
     "loader/fetch/MockResourceClient.h",
+    "loader/testing/FetchTestingPlatformSupport.cpp",
+    "loader/testing/FetchTestingPlatformSupport.h",
+    "loader/testing/MockFetchContext.h",
     "network/mime/MockMimeRegistry.h",
     "scheduler/base/task_queue_manager_delegate_for_test.cc",
     "scheduler/base/test_time_source.cc",
@@ -1744,12 +1747,9 @@ test("blink_platform_unittests") {
     "json/JSONValuesTest.cpp",
     "loader/fetch/ClientHintsPreferencesTest.cpp",
     "loader/fetch/CrossOriginAccessControlTest.cpp",
-    "loader/fetch/FetchTestingPlatformSupport.cpp",
-    "loader/fetch/FetchTestingPlatformSupport.h",
     "loader/fetch/FetchUtilsTest.cpp",
     "loader/fetch/MemoryCacheCorrectnessTest.cpp",
     "loader/fetch/MemoryCacheTest.cpp",
-    "loader/fetch/MockFetchContext.h",
     "loader/fetch/RawResourceTest.cpp",
     "loader/fetch/ResourceFetcherTest.cpp",
     "loader/fetch/ResourceLoaderOptionsTest.cpp",