Switch blink::FrameView to use downcast helpers

R=haraken@chromium.org
CC=blink-reviews-onion-soup@chromium.org

BUG=891908

Change-Id: I2783d2caf8b915a06bb5277d35ca650f079a58c7
Reviewed-on: https://chromium-review.googlesource.com/c/1483173
Commit-Queue: Antonio Gomes <tonikitoo@igalia.com>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#634709}

third_party/blink/renderer/core/frame/frame_view.h

@@ -6,6 +6,7 @@
 #define THIRD_PARTY_BLINK_RENDERER_CORE_FRAME_FRAME_VIEW_H_
 
 #include "third_party/blink/renderer/core/frame/embedded_content_view.h"
+#include "third_party/blink/renderer/platform/wtf/casting.h"
 
 namespace blink {
 
@@ -22,11 +23,12 @@ class CORE_EXPORT FrameView : public EmbeddedContentView {
   bool IsFrameView() const override { return true; }
 };
 
-DEFINE_TYPE_CASTS(FrameView,
-                  EmbeddedContentView,
-                  embedded_content_view,
-                  embedded_content_view->IsFrameView(),
-                  embedded_content_view.IsFrameView());
+template <>
+struct DowncastTraits<FrameView> {
+  static bool AllowFrom(const EmbeddedContentView& embedded_content_view) {
+    return embedded_content_view.IsFrameView();
+  }
+};
 
 }  // namespace blink
 

third_party/blink/renderer/core/layout/layout_embedded_content.cc

@@ -88,12 +88,7 @@ LayoutEmbeddedContent::~LayoutEmbeddedContent() {
 }
 
 FrameView* LayoutEmbeddedContent::ChildFrameView() const {
-  EmbeddedContentView* embedded_content_view = GetEmbeddedContentView();
-
-  if (embedded_content_view && embedded_content_view->IsFrameView())
-    return ToFrameView(embedded_content_view);
-
-  return nullptr;
+  return DynamicTo<FrameView>(GetEmbeddedContentView());
 }
 
 WebPluginContainerImpl* LayoutEmbeddedContent::Plugin() const {