[devtools] Add DOMSnapshot domain for dom+layout+style snapshots.

third_party/WebKit/Source/web/WebDevToolsAgentImpl.cpp

Index: third_party/WebKit/Source/web/WebDevToolsAgentImpl.cpp
diff --git a/third_party/WebKit/Source/web/WebDevToolsAgentImpl.cpp b/third_party/WebKit/Source/web/WebDevToolsAgentImpl.cpp
index 3a276ad6c5e729db648599291498b1ae0374be96..cfb592c924681037be44319b14ca36e4b2c8a4f8 100644
--- a/third_party/WebKit/Source/web/WebDevToolsAgentImpl.cpp
+++ b/third_party/WebKit/Source/web/WebDevToolsAgentImpl.cpp
@@ -50,6 +50,7 @@
 #include "core/inspector/InspectorCSSAgent.h"
 #include "core/inspector/InspectorDOMAgent.h"
 #include "core/inspector/InspectorDOMDebuggerAgent.h"
+#include "core/inspector/InspectorDOMSnapshotAgent.h"
 #include "core/inspector/InspectorEmulationAgent.h"
 #include "core/inspector/InspectorInputAgent.h"
 #include "core/inspector/InspectorLayerTreeAgent.h"
@@ -334,6 +335,8 @@ void WebDevToolsAgentImpl::InitializeSession(int session_id,
       resource_content_loader_.Get(), resource_container_.Get());
   session_->Append(css_agent);
 
+  session_->Append(InspectorDOMSnapshotAgent::Create(inspected_frames_.Get()));
+
   session_->Append(new InspectorAnimationAgent(
       inspected_frames_.Get(), css_agent, session_->V8Session()));