Add constructors to WebInputEvents and setters so we can work at cleaning up these public structs.

chrome/browser/referrer_policy_browsertest.cc

Index: chrome/browser/referrer_policy_browsertest.cc
diff --git a/chrome/browser/referrer_policy_browsertest.cc b/chrome/browser/referrer_policy_browsertest.cc
index d41ca45f3f461760119db45943ea8bfb871d5149..fedd897ca24519b7465291a43f0a95a62ebdbba0 100644
--- a/chrome/browser/referrer_policy_browsertest.cc
+++ b/chrome/browser/referrer_policy_browsertest.cc
@@ -177,14 +177,15 @@ class ReferrerPolicyTest : public InProcessBrowserTest {
     ui_test_utils::NavigateToURL(browser(), start_url);
 
     if (button != blink::WebMouseEvent::Button::NoButton) {
-      blink::WebMouseEvent mouse_event;
-      mouse_event.type = blink::WebInputEvent::MouseDown;
+      blink::WebMouseEvent mouse_event(
+          blink::WebInputEvent::MouseDown, blink::WebInputEvent::NoModifiers,
+          blink::WebInputEvent::TimeStampForTesting);
       mouse_event.button = button;
       mouse_event.x = 15;
       mouse_event.y = 15;
       mouse_event.clickCount = 1;
       tab->GetRenderViewHost()->GetWidget()->ForwardMouseEvent(mouse_event);
-      mouse_event.type = blink::WebInputEvent::MouseUp;
+      mouse_event.setType(blink::WebInputEvent::MouseUp);
       tab->GetRenderViewHost()->GetWidget()->ForwardMouseEvent(mouse_event);
     }