Remove PlatformEvent it is no longer used.

third_party/WebKit/Source/core/events/KeyboardEvent.cpp

Index: third_party/WebKit/Source/core/events/KeyboardEvent.cpp
diff --git a/third_party/WebKit/Source/core/events/KeyboardEvent.cpp b/third_party/WebKit/Source/core/events/KeyboardEvent.cpp
index 6e6b84795beb7c58f03d24558fd8f930a2183b1e..c2764772824dbf86a29cb9dfd0c565be310a6d74 100644
--- a/third_party/WebKit/Source/core/events/KeyboardEvent.cpp
+++ b/third_party/WebKit/Source/core/events/KeyboardEvent.cpp
@@ -94,7 +94,7 @@ KeyboardEvent::KeyboardEvent(const WebKeyboardEvent& key,
           true,
           domWindow,
           0,
-          static_cast<PlatformEvent::Modifiers>(key.modifiers()),
+          static_cast<WebInputEvent::Modifiers>(key.modifiers()),
           TimeTicks::FromSeconds(key.timeStampSeconds()),
           InputDeviceCapabilities::doesntFireTouchEventsSourceCapabilities()),
       m_keyEvent(WTF::makeUnique<WebKeyboardEvent>(key)),
@@ -114,7 +114,7 @@ KeyboardEvent::KeyboardEvent(const AtomicString& eventType,
       m_location(initializer.location()),
       m_isComposing(initializer.isComposing()) {
   if (initializer.repeat())
-    m_modifiers |= PlatformEvent::IsAutoRepeat;
+    m_modifiers |= WebInputEvent::IsAutoRepeat;
   initLocationModifiers(initializer.location());
 }
 
@@ -193,13 +193,13 @@ int KeyboardEvent::which() const {
 void KeyboardEvent::initLocationModifiers(unsigned location) {
   switch (location) {
     case KeyboardEvent::kDomKeyLocationNumpad:
-      m_modifiers |= PlatformEvent::IsKeyPad;
+      m_modifiers |= WebInputEvent::IsKeyPad;
       break;
     case KeyboardEvent::kDomKeyLocationLeft:
-      m_modifiers |= PlatformEvent::IsLeft;
+      m_modifiers |= WebInputEvent::IsLeft;
       break;
     case KeyboardEvent::kDomKeyLocationRight:
-      m_modifiers |= PlatformEvent::IsRight;
+      m_modifiers |= WebInputEvent::IsRight;
       break;
   }
 }