Extensions: Move cast_channel and hid APIs to extensions/.

extensions/browser/api/cast_channel/cast_channel.proto

Index: extensions/browser/api/cast_channel/cast_channel.proto
diff --git a/chrome/browser/extensions/api/cast_channel/cast_channel.proto b/extensions/browser/api/cast_channel/cast_channel.proto
similarity index 98%
rename from chrome/browser/extensions/api/cast_channel/cast_channel.proto
rename to extensions/browser/api/cast_channel/cast_channel.proto
index fd226541d5abdf22730b462ec9de946aa9b021d4..15574bd95299beb4bd80a9cca39b4c5f7d183d6f 100644
--- a/chrome/browser/extensions/api/cast_channel/cast_channel.proto
+++ b/extensions/browser/api/cast_channel/cast_channel.proto
@@ -6,7 +6,7 @@ syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 
-package extensions.api.cast_channel;
+package extensions.core_api.cast_channel;
 
 message CastMessage {
   // Always pass a version of the protocol for future compatibility
@@ -27,7 +27,7 @@ message CastMessage {
   //
   // For messages to or from the sender or receiver platform, the special ids
   // 'sender-0' and 'receiver-0' can be used.
-  // 
+  //
   // For messages intended for all endpoints using a given channel, the
   // wildcard destination_id '*' can be used.
   required string source_id = 2;