TestPlugin to chromium c++ style.

Changes:
1) Run clang-format through source and header files.
2) Rename data member variables to use unix_hacker_ style.
3) Rename methods to use CamelCase style.
4) Rename file name to test_plugin.

BUG=331299

Review URL: https://codereview.chromium.org/469943003

Cr-Commit-Position: refs/heads/master@{#293160}
diff --git a/content/shell/BUILD.gn b/content/shell/BUILD.gn
index bfff38e..412e889 100644
--- a/content/shell/BUILD.gn
+++ b/content/shell/BUILD.gn
@@ -129,8 +129,6 @@
     "renderer/shell_render_process_observer.h",
     "renderer/shell_render_view_observer.cc",
     "renderer/shell_render_view_observer.h",
-    "renderer/test_runner/TestPlugin.cpp",
-    "renderer/test_runner/TestPlugin.h",
     "renderer/test_runner/WebTask.cpp",
     "renderer/test_runner/WebTask.h",
     "renderer/test_runner/WebTestDelegate.h",
@@ -182,6 +180,8 @@
     "renderer/test_runner/test_common.h",
     "renderer/test_runner/test_interfaces.cc",
     "renderer/test_runner/test_interfaces.h",
+    "renderer/test_runner/test_plugin.cc",
+    "renderer/test_runner/test_plugin.h",
     "renderer/test_runner/test_runner.cc",
     "renderer/test_runner/test_runner.h",
     "renderer/test_runner/text_input_controller.cc",