Add CSS agent for various window/widget/view attributes in devtools

ash/common/wm_shell.cc

Index: ash/common/wm_shell.cc
diff --git a/ash/common/wm_shell.cc b/ash/common/wm_shell.cc
index 98cd1ce22545b277ab2d90a4e63d492738722820..8c64a651fac9e7a2e084feb71e11f6231bf007e9 100644
--- a/ash/common/wm_shell.cc
+++ b/ash/common/wm_shell.cc
@@ -9,6 +9,7 @@
 #include "ash/common/accelerators/accelerator_controller.h"
 #include "ash/common/accelerators/ash_focus_manager_factory.h"
 #include "ash/common/accessibility_delegate.h"
+#include "ash/common/devtools/ash_devtools_css_agent.h"
 #include "ash/common/devtools/ash_devtools_dom_agent.h"
 #include "ash/common/focus_cycler.h"
 #include "ash/common/keyboard/keyboard_ui.h"
@@ -92,9 +93,12 @@ void WmShell::Initialize(const scoped_refptr<base::SequencedWorkerPool>& pool) {
   devtools_server_ = ui::devtools::UiDevToolsServer::Create(nullptr);
   if (devtools_server_) {
     auto dom_backend = base::MakeUnique<devtools::AshDevToolsDOMAgent>(this);
+    auto css_backend =
+        base::MakeUnique<devtools::AshDevToolsCSSAgent>(dom_backend.get());
     auto devtools_client = base::MakeUnique<ui::devtools::UiDevToolsClient>(
         "Ash", devtools_server_.get());
     devtools_client->AddAgent(std::move(dom_backend));
+    devtools_client->AddAgent(std::move(css_backend));
     devtools_server_->AttachClient(std::move(devtools_client));
   }
 }