Extract WebWidgetTestClient out of WebTestProxyBase and WebViewTestClient.

components/test_runner/web_test_interfaces.h

Index: components/test_runner/web_test_interfaces.h
diff --git a/components/test_runner/web_test_interfaces.h b/components/test_runner/web_test_interfaces.h
index 1c9d55e178e3188233db7d6af604641a84dda4ae..362fe32b7261bf06f8d9d0972514880bb6a13622 100644
--- a/components/test_runner/web_test_interfaces.h
+++ b/components/test_runner/web_test_interfaces.h
@@ -36,6 +36,7 @@ class WebTestDelegate;
 class WebTestProxyBase;
 class WebTestRunner;
 class WebViewTestClient;
+class WebWidgetTestClient;
 
 class TEST_RUNNER_EXPORT WebTestInterfaces {
  public:
@@ -80,6 +81,13 @@ class TEST_RUNNER_EXPORT WebTestInterfaces {
   std::unique_ptr<WebViewTestClient> CreateWebViewTestClient(
       WebTestProxyBase* web_test_proxy_base);
 
+  // Creates a WebWidgetClient implementation providing test behavior (i.e.
+  // providing a mocked screen orientation).  The caller should guarantee that
+  // the returned pointer won't be used beyond the lifetime of WebTestInterfaces
+  // and/or the lifetime of |web_test_proxy_base|.
+  std::unique_ptr<WebWidgetTestClient> CreateWebWidgetTestClient(
+      WebTestProxyBase* web_test_proxy_base);
+
   // Gets a list of currently opened windows created by the current test.
   std::vector<blink::WebView*> GetWindowList();