[DevTools] Rework DevToolsSession interaction with domain handlers.

content/browser/devtools/protocol/dom_handler.h

Index: content/browser/devtools/protocol/dom_handler.h
diff --git a/content/browser/devtools/protocol/dom_handler.h b/content/browser/devtools/protocol/dom_handler.h
index 808af9c7ebd2531efc592a476808d5466edc1f6f..9ccf14064e592164967684163f1dd0b065fd95e7 100644
--- a/content/browser/devtools/protocol/dom_handler.h
+++ b/content/browser/devtools/protocol/dom_handler.h
@@ -6,6 +6,7 @@
 #define CONTENT_BROWSER_DEVTOOLS_PROTOCOL_DOM_HANDLER_H_
 
 #include "base/macros.h"
+#include "content/browser/devtools/protocol/devtools_domain_handler.h"
 #include "content/browser/devtools/protocol/dom.h"
 
 namespace content {
@@ -14,13 +15,14 @@ class RenderFrameHostImpl;
 
 namespace protocol {
 
-class DOMHandler : public DOM::Backend {
+class DOMHandler : public DevToolsDomainHandler,
+                   public DOM::Backend {
  public:
   DOMHandler();
   ~DOMHandler() override;
 
-  void Wire(UberDispatcher*);
-  void SetRenderFrameHost(RenderFrameHostImpl* host);
+  void Wire(UberDispatcher* dispatcher) override;
+  void SetRenderFrameHost(RenderFrameHostImpl* host) override;
   Response Disable() override;
 
   Response SetFileInputFiles(