Adds keyboard functionality for videos.

third_party/WebKit/Source/core/html/HTMLElement.cpp

Index: third_party/WebKit/Source/core/html/HTMLElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLElement.cpp b/third_party/WebKit/Source/core/html/HTMLElement.cpp
index e532670190f77722ec7c91dde98b7b54d088977f..b39d04e20cd291a7c4012ac9efbcb9da8bf7d4e8 100644
--- a/third_party/WebKit/Source/core/html/HTMLElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLElement.cpp
@@ -929,6 +929,10 @@ Node::InsertionNotificationRequest HTMLElement::InsertedInto(
   return kInsertionDone;
 }
 
+bool HTMLElement::IsSpatialNavigationActive() {
+    return IsSpatialNavigationEnabled(GetDocument().GetFrame());

[mlamouri (slow - plz ping), 2017/05/24 08:49:15]

Maybe just make this call in MediaControlsImpl instead of adding it to
HTMLElement?

[lethalantidote, 2017/05/24 18:46:08]

Tried doing that. It's not directly accessible due to BUILD visibility. Wasnt
sure if I should be messing with that (also tried and didn't figure out how to
get to visible. Willing to give it another go if this is preferable.) 

[mlamouri (slow - plz ping), 2017/05/30 10:22:41]

I think you would simply need to add CORE_EXPORT to `bool
IsSpatialNavigationEnabled(const LocalFrame*);` in SpatialNavigation.h and
include "core/CoreExport.h".

This should work:
`CORE_EXPORT bool IsSpatialNavigationEnabled(const LocalFrame*);`

You can find an example here:
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/dom/Range...

[lethalantidote, 2017/05/30 19:48:12]

Done. The example was very helpful to me.

+}
+
 void HTMLElement::AddHTMLLengthToStyle(MutableStylePropertySet* style,
                                        CSSPropertyID property_id,
                                        const String& value,