Monitor the intersection of video and viewport.

media/base/media_observer.h

Index: media/base/media_observer.h
diff --git a/media/base/media_observer.h b/media/base/media_observer.h
index c3e29a1789f173d2cc62ad12845392cfaf1a70f7..d5b214cdb945198408db5780a5d99d860a0b0e5d 100644
--- a/media/base/media_observer.h
+++ b/media/base/media_observer.h
@@ -7,6 +7,7 @@
 
 #include "media/base/cdm_context.h"
 #include "media/base/pipeline_metadata.h"
+#include "ui/gfx/geometry/rect.h"
 
 namespace media {
 
@@ -16,9 +17,21 @@ class MEDIA_EXPORT MediaObserver {
   MediaObserver();
   virtual ~MediaObserver();
 
+  struct ViewportIntersectionInfo {
+    ViewportIntersectionInfo() {}
+    ~ViewportIntersectionInfo() {}
+
+    float ratio = 0;
+    gfx::Rect root_rect;
+    gfx::Rect intersect_rect;
+  };
+
   // Called when the media element entered/exited fullscreen.
   virtual void OnEnteredFullscreen() = 0;
   virtual void OnExitedFullscreen() = 0;
+  // Called when the video/viewport ratio changed.
+  virtual void OnVideoViewportIntersectionChanged(
+      const ViewportIntersectionInfo& info) {}
 
   // Called when CDM is attached to the media element. The |cdm_context| is
   // only guaranteed to be valid in this call.