Implement window management devtools commands for headless.

headless/public/headless_devtools_client.h

Index: headless/public/headless_devtools_client.h
diff --git a/headless/public/headless_devtools_client.h b/headless/public/headless_devtools_client.h
index b3cea9482c32724c35fce69f4c58ead0b38495e3..1b8073e81b54d3a686e04502f526be5a08f29da5 100644
--- a/headless/public/headless_devtools_client.h
+++ b/headless/public/headless_devtools_client.h
@@ -21,6 +21,9 @@ class Domain;
 namespace application_cache {
 class Domain;
 }
+namespace browser {
+class Domain;
+}
 namespace cache_storage {
 class Domain;
 }
@@ -115,6 +118,7 @@ class HEADLESS_EXPORT HeadlessDevToolsClient {
   virtual accessibility::Domain* GetAccessibility() = 0;
   virtual animation::Domain* GetAnimation() = 0;
   virtual application_cache::Domain* GetApplicationCache() = 0;
+  virtual browser::Domain* GetBrowser() = 0;
   virtual cache_storage::Domain* GetCacheStorage() = 0;
   virtual console::Domain* GetConsole() = 0;
   virtual css::Domain* GetCSS() = 0;